ON-BOARD DIAGNOSTICS 

A few days ago I was driving behind a string of cars through Liesbeek Parkway when I was startled by several drivers repeatedly  hooting at an Audi A4 driving in front of them to get out of the way or change lane. The Audi A4 that was holding up the traffic had a Guateng registration plate and  my first impression was that its occupants got lost at the spaghetti junction fly-over, not knowing which off ramp to take.

However when these impatient hooting drivers finally overtook the Audi A4 and I got to drive behind it;  I then realized that the Audi A4 was in fact in Limp Mode. Its driver was attempting to get to the shoulder of the road from the centre lane and the traffic just wasn't easing up.

In my opinion, these impatient driver just weren't aware that when a vehicle goes into Limp Mode it cannot go any faster than it's already going even though its driver was flooring the accelerator pedal. And I may add that ignorance about Limp Mode is no excuse, because its been around since 1996.

Vehicle Delivery Services Salvaged Limp Mode car

DRIVER COURTESY

Driver courtesy is very important to bolster safe driving conditions for everyone but an education regarding Limp Mode would be considered far more important. When a car suddenly reduces speed after driving at normal speed, it could be one of several reasons; among which could be steering vibration due to a puncture. Or the vehicle ran out of fuel. Or the engine may have switched off due to a dead battery caused by either alternator issues or snapped fan belt. 

Or the engine may be overheating, or the driver heard a disturbing noise coming from the engine. Or it could be an electrical fault like a faulty fuel pump or an ignition system failure like a defective engine or transmission control unit. Or the driver could have fell ill behind the wheel, to mention but a few of the myriad of reasons why a vehicle could stall or it may have entered in Limp Mode. 

AUTOMATIC TRANSMISSIONS

The engines of cars with automatic transmissions can sometimes switch off mid travel for some obscure reason. The only option the driver has, is to pull off the road, bring the car to a halt, place it in park or neutral to restart the engine. I know of someone who shifted his automatic transmission into neutral when the engine cut out mid travel, restarted the car and shifted it back into drive. This caused his car to almost come to a stand-still instantly causing the wheels to screech as the engines inhibited the transmission.  This type of action can and probably will damage the transmission subject to the gearing system inside and should never be done. Unfortunately no On-board diagnostics makes provision to prevent this.

When an engine cuts out at say 100kph both the power steering and vacuum boosted brakes stops working, thereby making steering difficult and the braking inefficient. It is therefore best to pull off onto  the shoulder of the road and check what the problem is an remedy it before continuing on your journey.

ON-BOARD DIAGNOSTICS

On-Board Diagnostics does a pretty decent job of protecting the engine and transmission against damage by limiting  acceleration, keeping the engine revs to a maximum of 2000 (RPM) and speed to about 45kph - aka Limp Mode. When Limp Mode is enabled, it may lock an automatic transmission  in low gear and even disable both heating and air conditioning. Yet keeping the engine running so that it can be driven to a repair shop.

However, as clever as an ECU is,  it doesn't do anything to alert the driver of the car that follows close behind. Considering tail lights, brake light, reverse lights and  indicators represents a language used by vehicle drivers for those  following behind, to indicate their driving intentions. This light language that's been around for the better part of the automotive industry's existence yet it still haven't come-up with an appropriate and safe warning sign/method for Limp Mode. 

LIMP MODE INDICATOR

To remedy this, car manufacturers could include flashing hazard lights or perhaps fit an LED Display with a scrolling message along the the rear window as an alert to tell the driver following behind that the car in front of it has gone into Limp Mode. Alternatively, electronics savvy car owners can fit their own aftermarket hack by identifying the switching output of the appropriate automotive  High Side Switch (HSS) responsible for protection and diagnostics inside the ECU when Limp Mode is enabled.

Automotive industry High-Side Switches /Drivers - Integrated Circuit 

This may not be as easy as it may seem or sounds because of the myriad of automotive chip manufactures, each pushing their our integrated circuits (ICs) running custom/propriety software, among which are Infineon Technologies AG,   Robert Bosch, Qualcomm, Renesas Electronics Corporation (Intersil), NXP Semiconductors,  STMicroelectronics, Texas Instruments, Intel and Microchip Technology Inc, etc.

However, most of these manufacturers produce Power Switches and incorporate Open Load Detection in their design so that they can perform open-circuit diagnosis on loads, such wiper motors, fans, head lamps, fuel pump, mirrors, actuators in general and LED lights while  the load is enabled or disabled. Open load diagnosis is probably the most important function of the software driven High-Side Switch (HSS) and Low-Side Switch when wired in a specific configuration which allows for currents from 5mA to more than 10A to be accurately detected.   

As such able to generate a hardware signal (Limp Mode signal) that can directly control the hardware without the participation of the microprocessor in the ECU. This output can be used to as either a digital High of Low (using CMOS inverter) to drive a LED display that flashes LIMP MODE..... LIMP MODE..... LIMP MODE.....

That EPC light.

The most likely reason you're reading this blog post, is because you encountered an EPC fault with your Volkswagen vehicle. I bet you wondered what that yellow/orange light was when it lit-up or perhaps startled when you car went into "limp mode". Whether you're driving a VW Polo or VW Jetta, VW Golf,  VW Caddy, VW Passat, T-Cross, Sharan, Touareg, Transporter, or any other Volkswagen or even a German Audi, or a Czech Skoda or a Spanish VW SEAT, you've come to the right place because they all have an  Electronic Power Control circuit. 

In fact all "modern day" vehicles have EPC circuit, which loudly says that the automotive industry have finally reached some consensus on standardization. But let me tell you what the EPC light actually is. It's just a signal light informing you that there is an error in your vehicles torque circuit. That's the short answer, however, I can tell by the look on your face that it wasn't a  satisfactory answer, so let me give you the long version.

The EPC light is part of the Electronic Power Control Circuit which is just one of the components of OBD-II which was mandated by a certain regulatory bodies with regulatory intent. Their initial intention was to limit carbon emissions / exhaust fumes from cars on the street of America. 

The California Air Resources Board (CARB) and the Environmental Protection Agency (EPA) together with the Society of Automotive Engineers (SAE) and the International Organization for Standardization (ISO) collectively originated the On-Board Diagnostic (OBD) System because of high levels of smog produced by automobiles throughout the USA.  

Their initial On-Board Diagnostic System was subsequently superseded by the all new and improved verion OBD-II, hence all cars manufactured post 1996 has an Electronic Power Control Circuit and by extension an EPC light. The European on-board diagnostics (EOBD) regulations are the European equivalent of the American OBD-II. 

On-Board Diagnostic (OBD-II) is an automotive mechatronic, micro processor / micro controller based computer system with programmed presets that continuously monitors inputs from numerous sensors fitted through the car. 

It then computes/compares/ compensates these inputs against stored data and drives various actuators to perform certain tasks. In a nutshell OBD-II is an input/output (I/O) information processing system much like the PC / laptop / or even your smart phone. By example, a keyboard, a mouse, a joystick, a scanner and a microphone are common computer input devices whereas a HD monitor, a printer, speakers and headphones are common computer output devices. 

Here the computer/laptop makes calculations based on its internal operating system and software to do something intelligible for humans. However in the case of OBD-II, its CPU (Central Processing Unit) is called an ECU (Electronic Control Unit) and among its input sensors are the Accelerator Position Sensor, Mass Air Flow sensor (MAF), Lambda O2 Sensor, Knock sensor, Oli level sensor, Coolant Temperature Sensor, the Camshaft Position Sensor, the Crank Position Sensor, the Wheel Speed  Sensor etc, to mention but a few.

Among its output actuators and solenoids are the drive-by-wire electronic throttle actuator, the fuel injectors, the EPC light, Malfunction Indicator Light (MIL), the Immobilizer, the Airbags and the Power Steering Pump, etc, again to mention but a few,

This ECU is sometimes referred to as an Engine Control Unit especially when intending to make reference to the TCU (Transmission Control Unit). The ECU is sometimes even called ECM (Engine Control Module) when making reference to other electronic control modules like the ABS module, the Instruments module, the Central Electronics Module, the CAN gateway module, the Radio Module, etc, again to mention but a few 

However, the ECU and the TCU are collectively referred to as Powertrain Control Module (PCM). The ECM essentially controls the efficiency of the engine performance by using a Crankshaft Position Sensor to determine the position of the cams in order to activate the injection of fuel into the cylinders and the timing of the ignition spark to ignite it at precisely the correct moment in petrol engines. 

Likewise the ECM in Diesel engines, plays a huge role in the success of the turbodiesel models. But in order for this to happen, an electronic throttle control had to be introduced, replacing the  cable from the pedal to the carburetor system which was prone to idle speed deviation between a hot and cold engine that became more and more prevalent as the components wore out. 

In so doing, the ECM can adjust the electronic throttle angle during acceleration to achieve the right quantitative relationship ratio between the actual airflow through the engine and the injected fuel thus maintaining Stoichiometry. Controlling the throttle airflow on the fly, markedly improves overall torque and driveability which is known as torque-mapping, an advantage that is only possible with drive-by-wire. 

So, the Electronic Power Control Circuit consists of the ECM, the Accelerator Position Sensor, the Throttle Position Sensors, the Throttle Actuator, the MAF / Air Filter, the Fuel Injectors, the High Pressure Fuel Pump, Fuel Temperature Sensor, Fuel Rail Pressure Sensor and Pressure Relief Valve. 

The single accelerator position sensor is made up of two individual potentiometers each acting independently of the other but collectively operate with opposite polarity voltages supplied by the ECM, as a safety back-up for one another. 

Thus, if either potentiometer fails, the ECM will activate limp mode. This is a safety measure that prevents the system from acting as if it had an accelerator cable that got stuck in the runaway position and the makings of a potential accident. The cruise control also has influence on the throttle body and requires the brake pedal to be depressed to cancel the cruise control. 

The ECU normally takes this cancellation signal from the brake light MOSFET low-side driver in the ECU. So either the brake pedal switch and the a brake light bulb can cause an EPC error along with the aforementioned fuel supply components. It's best to have a diagnostic tester to check for DTC errors via the DLC connector. It would at the very least steer you in the right direction to fix your EPC problem effectively.

Common OBD-II Problems

OBD-II has now been in our faces for a "Quarter Century" and even though it works fairly efficiently to control the hydro-carbon emissions in post '96 vehicles to some degree, it isn't as effective as some people would've liked, in terms of its diagnostic accuracy or as transparent and simplistic in its use to aid the layman.  On the flip side, many people with several mechanics among them completely abhors OBD-II and sees it more as a hindrance that a help and even add that they prefer cars not to have OBD-II. Since its inception, OBD-II has stymied mechanics globally, especially when the OBD-II system shuts down the engine and turns on the  EPC Light or Check Engine Light. And today, some 25 years later most car owners and mechanics still suffer fits effects yet endure the wrath of OBD-II. However, regardless of what we as lay people say, OBD-II is here to stay and we cannot wish it or will it away. 

Genuine Volkswagen / Audi Harness Mfg Part #: 1KD971658

Personally I think OBD-II is a great in all aspects and incarnations however it has its drawbacks. OBD-II  does place car owners at a huge disadvantage and at risk when it fails. Purely because the problems are not evident but rather masked by the mysteries of electronics technology. This very often leaves them stranded and in a dangerous situations when stuck in the middle of nowhere. With the result that even the DIY car owners cannot do any repair work themselves, but have to resort to phoning  a salvage company to come  load their vehicle onto  a rollback.  Unless of course they have previously invested in a OBD-II scanner  and is able to check for DTC error codes.  But as the saying goes, "most people only lock the stable after the horse has bolted". 

Another drawback of OBD-II is that since car owners in general do not own diagnostic scanners; so they have to rely on some mechanic workshop or mechanical to tell them what problems they've encountered with their vehicle but only once its repaired. Considering most mechanics / repair shops repair OBD-II errors by substituting parts until the cause of the problem is  solved. Merely because they don't even understand the workings of OBD-II well enough to pinpoint problems with any great success. For most of us, this type of hit-&-miss approach comes as an un-bugeted expense, which most car owners can ill-afford especially after having to pay the exorbitant rollback cost.

I believe there are thousands more vehicle owners today, interested in their own vehicle's maintenance and there are even more inclined towards DIY repairs than ever before because of ODB-II. Their motivating factor being the high cost of automotive repairs vs the low cost of ODB-II diagnostic scanners. Albeit that the lower cost scanners bordering on cheap doesn't do such a fantastic diagnostic scan as their more expensive counter parts. 

NEW GENERATION CARS

Hopefully, the next generation of automobiles will be released with onboard diagnostic scanners incorporated directly into the vehicle's infotainment system. Seeing that these fancy units are comprised of  several discrete devices built into the same platform.  It's quite common for the average touch screen infotainment systems to have features ranging from  Built-in Bluetooth to Built-in WIFI which supports WiFi hot-spot broadcasting. Integrated phone connectivity for calls. Some even have rear view camera support. 

Others have fully fledged full-format 1080P video decoding, and USB functionality with multi-format audio and multi-band radio, coupled to dedicated dual voice-coil subwoofer and surround sound speakers. Not to mention Internet APP download capability.  Some include mirror and link for both Android and IOS Phones and a Global Positioning System (GPS) for navigation. All thanks to the magic of powerful multi-core processors and microprocessor embedded systems. 

I'd say adding an OBD-II scanner in place of one of these gadgets would be more beneficial 

So, throwing in a pretty decent quality OBD-II scanner into such a menagerie of tech wouldn't be such a biggie for car manufacturers and the cost wouldn't be prohibitively expensive either.  But since we not at that point in automotive evolution as yet, most DIY car owners have to rely on the handheld / smartphone diagnostics to scan their cars. 

Be that as it may. Very fortunately there are some common fault lists that would prevent you from having to go buy an expensive OBD-II scanner or go through the agony and trauma of having your car fixed by trial and error. Sharing  common automotive problems for the benefit of other, who are bound to experience the exact same problems in the very near future is a godsend.  Same model cars tend to have the same problems as others but invariable and inevitably those components will fail because obsolescence was part of its initial design. The same components used different model cars tend to fail in the same way and cause the same problems.

We've found that the most common OBD-II problems are associated with misfiring engine cylinders, problematic exhaust Gate Reticulation system (EGR), Oxygen Sensor (O2), Electrical Harnesses and fault Catalytic Converters. Many car owners are decating their diesel models, claiming better performance. But since OBD-II was explicitly introduced to control and reduce carbon emissions, removing it is not such a great idea. 

VW / Audi Harness ES#: ES2993475  

 

COMMON FAULTS 

Erratically idling, or misfiring of bucking or  car goes into limp mode or starts and cuts out all result any one or more of the following error codes:-

P0105 - Manifold Absolute Pressure / Barometric Pressure Voltage supply

P0106 - Manifold Absolute Pressure / Barometric Pressure out of range 

P0107 - Manifold Absolute Pressure / Barometric Pressure Low Input

P0108 - Manifold Absolute Pressure / Barometric Pressure High Input

P0234 - Turbocharger Overboost Condition Control limit exceeded

P0235 - Turbocharger Boost Sensor (A) Control circuit  limit not reached

P0236 - Turbocharger Boost Sensor (A) circuit  out of range

P0237 - Turbocharger Boost Sensor (A) circuit  Low Input

P0238 - Turbocharger Boost Sensor (A) circuit  High Input

P0243 - Turbocharger Wastegate Solenoid (A) Open/Short Circuit to Ground

P0245 - Turbocharger Wastegate Solenoid (A) Low Input/Short to ground

P0246 - Turbocharger Wastegate Solenoid (A) High Input/Short to B+

P1154 - Manifold Switch Over Malfunction

P1155 - Manifold Absolute Pressure Sensor Circuit Short to B+

P1156 - Manifold Absolute Pressure Sensor Circuit Open/Short to Ground

P1157 - Manifold Absolute Pressure Sensor Circuit Power Supply Malfunction

P1158 - Manifold Absolute Pressure Sensor Circuit  out of range

P1400 - EGR Valve Circuit  Electrical Malfunction

P1401 - EGR Valve Circuit  Short to Ground

P1402 - EGR Valve Circuit  Short to B+

P1403 - EGR Flow Deviation

P1404 - EGR Flow Basic Setting not carried out

P1406 - EGR Temperature Sensor Performance range

P1407 - EGR Temperature Sensor Signal too Low

P1408 - EGR Temperature Sensor Signal too High

P1511 - Intake Manifold Changeover Valve - Electrical circuit malfunction

P1512 - Intake Manifold Changeover Valve Short circuit to B+

P1513 - Intake Manifold Changeover Valve2 Short circuit to B+

P1514 - Intake Manifold Changeover Valve2 Short circuit to ground

P1515 - Intake Manifold Changeover Valve Short circuit to ground

P1516 - Intake Manifold Changeover Valve - Open circuit 

P1520 - Intake Manifold Changeover Valve2 - Open circuit 

P1521 - Intake Manifold Changeover Valve2 electrical circuit malfunction

P1553 - Barometric/manifold pressure signal ratio out of range

Polo Highline 1.9 TDI (9N) 2005

16621 - Manifold Pressure / Boost Sensor (G31): Signal too Low

P0237 - 000 - -

Audi A5 (8T0) 2012 

4166 - Manifold Pressure / Boost Sensor (G31)

P0238 00 [039] - Signal too High

Audi TT 1.8L R4/5VT 

16622 - Manifold Pressure / Boost Sensor (G31): Signal too High

0238 - 35-00 - 

000568 - Manifold Pressure / Boost Sensor (G31): Signal too High

P0238 - 001 - Upper Limit Exceeded - MIL ON

Passat 2.0T R4/4V TFSI 2006 

000568 - Manifold Pressure / Boost Sensor (G31): Signal too High

P0238 - 001 - Upper Limit Exceeded - MIL ON

VW Touran 1.9 TDI

P0236 - Manifold Pressure/Boost Sensor (G31) - Range/Performance Problem/Implausible Signal

Malfunction Indicator Lamp (MIL)(K83) active.

VW Golf 7 1.6TDI 

16622 (P0238 ) - Manifold Pressure/Boost Sensor (G31): Signal too High

16618 (P0234) - Boost Pressure Regulation: Limit Exceeded (Overboost Condition)

Passat 2.0T R4/4V TFSI 2006 

004759 - Pressure Drop between Turbo and Throttle Valve

P1297 - 001 - Upper Limit Exceeded

This MAP Manifold Pressure Sensor aka Boost Sensor aka Thrust sensor  aka G31 is just a  thermistor. Essentially a resistor of a special kind, with the ability to change its resistance  subject to its surrounding temperature, hence the term thermistor is just a  word combination of "thermal" and "resistor".  However G31 sensor may not be fault but rather the wiring harness. Due to the constant engine heat, the harness wiring gets hard and becomes brittle resulting in poor contact, short and open circuits. 

FYI - Thermistors essentially come in two varieties, viz NTC (negative temperature coefficient) and a PTC (positive temperature coefficient). You can quite simply use an ohmmeter to measure the resistance of the thermistor. Then by bringing a hot soldering iron  tip close to the thermistor, its resistance would change in response to the soldering iron's radiated heat. When the resistance increases its a PTC and an NTC when the resistance decreases.  Much like discrete component resistors that are colour coded, thermistors leads are also colour coded which identifies the temperature range they operate at.

CATALYTIC CONVERTER

Catalytic Converter have become a hot topic of late. Thieves are stealing Catalytic converters from parked cars at night. However the Polo Highline 1.9 TDI is known to be troublesome. The main reason for  this being, use of poor quality diesel (500ppm as opposed to 50ppm or even 5ppm) and irregular oil changes  which caused soot build-up to block the performance of the catalytic converter, which in turn may lead to turbo failure.  So its fair to say that it's  not uncommon to remove/replace blocked catalytic converters  to prolong the life of the turbo itself.

However if it's not the Catalytic converter itself causing the above error,  it very possibly not the sensor either even though the diagnostic software may indicate that.  I'd say rather check, repair or replace the wiring harness to the Boost Pressure Sensor (G31) and also check wiring to the Intake Air Temperature Sensor (G42).  See my previous blog post https://volkswagen-polo-highline.blogspot.com/2015/03/wiring-harness-issues.html 

The diagnostic scanners may also thow the following errors in conjunction with the error above,  which could be caused by a leak in Air Intake and or Exhaust

16490 - Manifold / Barometric Pressure Sensor (G71) / (F96): Implausible Signal

P0106 - 35-00 - -

18000 - Altitude Sensor / Boost Pressure Sensor: Implausible Correlation

P1592 - 000 - -

Diesel engines are quite different from petrol engines in the sense that  the diesel engine is not variable in speed or power by controlling the air entering the engine as we do with the  throttle body in petrol styled engines. Feedback from Catalytic converter in petrol engines are also used to adjust the short term and long term fuel trim. Implying that petrol cars also have turbo boost errors due to the cat and intake and exhaust sensors.

16485 / P0101 Mass Air Flow Sensor (MAF) (G70) = Circuit Signal Implausible (out of range)

16497 / P0113 Intake Air Temperature  Sensor-1 (G42) = Signal too High

16515 / P0131 O2 (Lambda) sensor low voltage =  Bank-1 Low Voltage

16584 / P0200 Injector circuit =   Injector Circuit electrical fault

16620 / P0236 Turbo / Manifold Pressure Boost Sensor (G31) = Signal Implausible (out of range)

16622 / P0238 Turbo / Manifold Pressure Boost Sensor (G31) = Signal too High

16683 / P0299 Turbo Boost Pressure Reg = Control Range not reached (underboost) /mechanical fault

16785 / P0401 Exhaust Gas Recirculation (EGR) = Insufficient Flow (blocked)

17055 / P0671  Glow Plug/Heater Cylinder 1 (Q10)  electrical fault, open circuit 

17958 / P1550 code = Charge Pressure Control Deviation

Check for air leaks on both intake or exhaust side 

Turbocharger - check for whining engine and exhaust smoke

Charge Air Pressure Sensor faulty  - check connection to one of the the intercooler pipes

Wastegate Regulator N75 Valve  faulty  - Check one of the 3 thin hoses for leaks

18534 / P2102 Throttle  Actuator Control Motor = Signal too Low, check voltage to accelerator pedal 

18675 / P2243 O2  Sensor Reference Voltage Bank 1, open circuit 

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EPC issues

EPC Issues

EPC complaints have become the most common Volkswagen fault and outstrips check-engine-light three to one. It is one of the most tiresome and frustrating  faults to diagnose and repair because the only way of knowing that your most recent repair cured your EPC problem, is when it does't occur in the same situation under the same conditions thereafter. Mechanisms generally refer to Electronic Power Control (EPC) faults as evil, a waste of time and the cause of embarrassment.

Many disillusioned VW car owners can confirm that they've taken their vehicle to at least 2 different workshops to fix their respective EPC light problem. Often wanting a refund from the first workshop as they didn't fix the EPC issue, but only said they did. It's also known fact that tons of spare parts suspected of causing EPC have been replaced that didn't need replacing in the first place. Trial and error EPC repair seems to be the order of the day among motor mechanics. Even the agents are guilty of this and VW car owners are generally fed-up of mechanical and electronic competence. Many car owners and DIY mechanics are longing for the days when cars had a lot less electronics, were easier to diagnose and repair and one didn't need a degree in automotive engineering to replace something as meager as a MAF sensor. The word EPC among many others, is just one of the mechanical jargon that has come to invade the car industry. There are so many; to list just a few. Several of them capable of throwing an EPC light.

AIR: Air Injection System
ACC: Adaptive Cruise Control
ABS: Antilock Braking System
AWD: All-Wheel Drive
BHP: Brake Horsepower
CEL: Check Engine Light
CO2: Carbon Dioxide
CKP: Crankshaft Position Sensor
DLC: Data Link Connector
DDI: Direct Diesel Injection
DPF: Diesel Particulate Filter
DRL: Daytime Running Lights
DTC: Diagnostic Trouble Codes 
DSG: Direct-Shift Gearbox
ECT: Engine Coolant Temperature
ECU: Electronic Control Unit
EGR: Exhaust Gas Recirculation
EPA: Environmental Protection Agency
ESC: Electronic Stability Control
ESP: Electronic Stability Program 
FSH: Full Service History
FWD: Front Wheel Drive
IAT: Intake Air Temperature
KPH: Kilometres Per Hour
LED: Light Emitting Diode
LSD: Limited Slip Differential
LPG: Liquid Petroleum Gas
LWB: Long Wheelbase
MAF : Mass Air Flow (sensor) 
MAP: Manifold Absolute Pressure
MIL: Malfunction Indicator Light
MPV: Multi-Purpose Vehicle 
OBD: On-board Diagnostics
PCM: Powertrain Control Module
RPM: Revolutions Per Minute
RWD: Rear Wheel Drive
SUV: Sport Utility Vehicle
TDC: Top Dead Center
TCS: Traction Control System
TCU: Transmission Control Unit
TPS: Throttle Position Sensor
VCM: Vehicle Communications Module 
VIN: Vehicle Identification Number
VRM: Vehicle Registration Mark
WOT: Wide Open Throttle

The letters EPC in the automotive sector initially meant Electronic Parts Catalogue. Recording every conceivable component used in the  manufacture of that car, listed in alphanumeric order. Some EPC are exclusively online versions, or downloadable as pdf. Some cover specific cars  and others cover several makes of cars and is normally free, whereas the more elaborate EPCs with specialist automotive service data is charged for per search or as a monthly subscription.

For example, the ETK 2018 EPC  is specific to BMW,  Rolls Royce, Mini and the Chinese Zinoro which is the luxury automobile brand owned by BMW Brilliance specializing  in electric vehicles. ETK comes at an exorbitant price, in either downloadable or CD/DVD form. The Volkswagen  ETKA online /  ELSAWIN EPC is specific to Volkswagen, Audi, Seat and Skoda and spans 6 CDs and is also fairly expensive. It is an encyclopediac like compendium covering VW, Audi, Seat and Skoda vehicles manufactured between 1947 and 2018 in varying degrees of detail. 

It also includes the actual service & repair software used by factory technicians at Volkswagen, Audi, Seat, Skoda and their dealer workshops throughout the world. As such it would be in indispensable resource for the Volkswagen enthusiast but is also overkill for most. However most modern day cars have an EPC circuit which essentially deals with the torque of the vehicle. Using one of these catalogues and its diagnostic diagrams to identify these components and problems is one of the easiest ways of fixing EPC problems. To fix your EPC problem, click here, here or here.

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VW Fuses Switches and Relays

VW Fuses  Switches and Relays

Single Pole Single Throw

Electrical switches comes in several configurations, but are normally classified into only four types. The most common switch is the single pole single throw, abbreviated as SPST. This implies it has one contact that is normally open —abbreviated N/O—  which is closed when the switch is flicked. This type of switch is either on-or-off / open circuit or closed circuit. This switch also comes in the form of a push button switch which is normally open and closes when pushed but when released it open once again. It is also known as push-to-make, abbreviated PTM. An example of a PTM is a door bell switch or a cars hooter or the individual keys on a keyboard. Push button switches also comes in a normally closed configuration and opens when pushed, but when released, it closes again. Commonly  known as push-to-break, abbreviated PTB. An example of a PTB switch is used to release a door, held closed by an electromagnet.

Suzuki GS500 GSXR1100, Honda  VT 500 VT600 VT700 VF750,
Kawasaki ZX1000 ZX 1100 Solenoid

Single Pole Double Throw

The second and slightly more advanced switch is the single pole double throw switch, abbreviated as SPDT. This is a three terminal switch which toggles between two states when switched. SPDT are in essence two switches in one package. The one switch is normally open whilst the other is normally closed. By flicking the switch the two switches reverses their roles. The normally open switch is then closed and the normally close switch is opened. By connecting a SPDT at either end of a long passage to turns the lights or off, one is able to enter the passage at one end, turn the lights on and when exiting the passage at the other end switch the lights off. SPDT can be used as a SPST in an application by just using the centre contact and either one of the other two contacts, depending on what type of switch you need, N/O or N/C.  SPDT switches are also available with a centre-off position, known as momentary (ON)-OFF-(ON) switch.

Volkswagen 4H0951253 Starter Relay 645 and 1J0906381A Fuel pump relay 109. 

Double Pole Single Trow

The third type of switch is the DPST and is similar to the SPST switch in operation except that it has a pair of on-off switches that switch together. It is commonly used to connect / interrupt both the live and neutral supplies in a circuit simultaneously or it may be used to switch two separate circuits simultaneously. Computer power supplies have DPDT switches as a safety feature to avoid getting electrocuted whilst working on the power supply if only one pole was switched. 

Double Pole Double Throw

The fourth type of switch is the DPDT and is similar to the SPDT switch in operation except that it has a pair of on-on switches that switch together. It is commonly wired to reverse the direction of a DC motor or be used to switch between to different colour LEDS. DPDT can be used as a DPSP in an application by using the centre contact and either one of the other two contacts and duplicated on the paired switch. DPDP switches are also available with a centre-off position, known as momentary (ON)-OFF-(ON) switch.

Switches 

Switches switches come in various shapes among which are Toggle switches, limit switches, reed switches, micro switches, mercury switches, rotary switch, slide switch, rocker switch, pneumatic limit switches, selector switches and getting the right switch for the job cam sometimes be tricky and may be better suited by using a relay. Many switches also come with a rubber jacket to make it  waterproof. However that doesn't imply you can submerse the switch in water, it is more a splash proof cover than a water proof one. There are switches suited for using under water, for example a floating mercury switch. when a vat or tank is filled with liquid, the switch would float in the upright position but when the liquid falls below a certain lever  the switch would float upside down and trigger. Perhaps turning on a pump that would fill the tank or vat once again.

Whats a relay?

Having discussed switches you may ask what does switches have to do with relays. The simple answer is, a relay is essentially a remotely controlled switch. Relays are controlled electrically rather than mechanically, hence they're known as electro-mechanical relays. They are commonly used in automotive design, where high current devices can be switched from a cockpit fairly cheaply. In stead of using long lengths of thick high current cable and a substantially heavy duty on-off switch to control a heater or a motor situated some distance from the driver; a small low current switch and a length of thin low current cable and a relay switch with heavy contacts would suffice. Every relays has a solenoid configured as an electromagnet. So when the solenoid is activated by a trigger voltage, the electromagnet pulls a set of heavy duty contacts to make or break a circuit. Relays are versatile and can function as a simple spst switch, or a more advance spdt switch of a dpst switch or a dpdt switch depending on the circuity it needs to control.

Volkswagen Solenoids

Sometimes you may need a switch with more contacts than the best switch you can find, and this is where relays outweigh switches. Relays also cost less than the combines cost of all the switches that it replaces or that can do the job of.  Volkswagen have several relays throughout its electrical system and the most hardworking relay, is the starter relay.  Starter relays form part of the starter, the reasoning, is to keep high current conductors as short as possible. However many cars have a second relay inserted into the fuse panel that powers the starter solenoid. So when you turn the ignition key to start your car, the starter relay contacts in the fuse box sends 12V to the starter solenoid on the starter. This solenoid's contacts throw and sends 12V from the thick battery cable that's connected to one side of the starter solenoid directly to the starter's field coils, causing its armature  to spin. But at exactly the same time the solenoid performs a dual function as it kicks the bendix forward into the ring gear's teeth.  The starter's force of rotation is sufficient to crack the engine and if all's well, the engine with start. 

The Definitive EPC Guide 2

The Definitive EPC Guide (Continued)

For part ONE Click Here!

Having said that, in my humble opinion, the  EPC circuit with its drive-by-wire circuit and its "Limp-mode home" mode, is a value-add for modern car design; and though frowned upon by many, is a very valuable safety feature. Also bearing in mind that when the communication network is momentarily unavailable and an application that depends on it is unable to communicate, it may trigger the ECU into "Limp-mode home" and set a DTC. Exception errors do occur in  synchronous or asynchronous distributed system, where software entities act as clients or servers or both. So when where 1...n clients are requesting services via a specific protocol from typically one server; the server services the client  but  temporarily blocks its service request and data flow control, whilst other client expects a response from the server.  

If 1 client to n server communication can be established, it would certainly solve the problem but it’s currently not supported. Also remembering that the CAN bus is a serial communication network through which all modules communicate with the ECU via a Central Gateway, some uses FlexRay frames and others Lin bus or CAN, each with a differing topology, some synchronous and others asynchronous. The Central Gateway is responsible for frame or signal mapping function between two communication systems, like from LIN/MOST/CAN/FlexRay to Ethernet transport systems. However ECU gateways often have two or more internal Gateways like the Service Data Unit (SDU) gateway, Layer 3 Tunnelling Protocol (L3TP) gateway and the Signal Gateway needed for frame or signal mapping function between two disparate communication systems.

The best analogy with which to explain the above would be your cell phone. Cell phones are native Global System for Mobiles (GSM) devices with a microprocessor and its support chips, much like the automotive ECU. Cell phones support the Hypertext Transfer Protocol (HTTP) and the Wireless Application Protocol (WAP) for Wi-Fi as well as the Bluetooth communications protocol through a "Gateway" which translates it to a common data stream native to the Cell phone operating system. 

So, while you’re downloading an email and the phone rings and you answer; the email download temporarily stops but will resume when the call is terminated. The same applies to a Bluetooth file transfer which will be interrupted even possibly terminated when a phone call is answered. However, not all services are prone to such interruptions because some services are inherent to the design. For example, when you’re listening to music on your cell phone and you answer an incoming call, the music is temporarily suspended until the call is terminated then the music will resume. 

This function is purposely part of the design whereas exception errors are not and are more prone to happen with asynchronous communication, caused by propagation delays. This is what also happens when the ECU inter communicates with other modules and when the messages are not delivered within a prescribed period of time, can cause the car to go into "Limp-mode home" . So if for some reason the radio that is a non-essential service is hogging the network bus, and you step on the brake which the ECU will undoubtedly detect but the brake light didn't illuminate within the expected response time, which the ECU will also detect, then the car may go into "Limp-mode home" . 

Or you could hit a speed bump in the road at high speed and bounce back onto the road; the thump if hard enough or loud enough to trip a knock sensor would cause the car to go into "Limp-mode home" . Or you could have just done some high rev spirited driving to cause the car to go into "Limp-mode home" . One consolation is that, when the ignition is initially turned on; right before the car is started the ECU does a self-test to verify that all’s well, and if that is the case, the car will start and drive normally. 

However, if the self-test fails, one of the caution lights may remain on. It could be either the EPC light or the Check Engine light or perhaps both, or one or both could be blinking, which is a sure sign that you may have a problem. Once again, a diagnostic scanned would be the most informative way of establishing what the problem is. But I’ve encountered car owner who took their vehicles for diagnostic tests and no errors were flagged, so in some cases may be a futile exercise. 

Having said that, if you are stranded along the road side, the best would be to reset the ECU by removing the battery earth terminal for a minute or two, but make absolutely certain that you have access to your radio / DVD code before  you disconnect. Whatever errors occurred prior to this will be safely stored in the ECU non-volatile memory and may be checked when a diagnostic scanner is available but all stored values will be lost.  The downside of doing this, is that an additional error would be flagged because the battery (+30V) supply was interrupted, and now the ECU has to relearn your driving style.

ECUs are fairly robust and are more-likely-than-not the cause of your EPC problems, though unlikely but not impossible.  The most likely component in my humble opinion that would cause constant and annoying EPC problems would be the wiring harness. Not the actual wires, unless they are frayed and damaged by rubbing against the chassis but rather its edge connectors. 

The ECUs and associated modules each have multi-pin connector that’s tin plated and can become intermittent due to the constant vibration of the car. Copper contacts also oxidizes fairly quickly, so to prevent this from happening, they are tin plated which provides for a low resistance, good contact surface. However when water enters this connection, especially in the presence of a voltage or current flow, the contact normally turns black or corrodes green, impeding continuity hence connectivity. 

A poor vehicle ground connection is another culprit that can intermittently trigger the EPC light without leaving a DTC.  A blown tail light / brake light bulb can also cause the EPC light to turn on without leaving a DTC. Always make sure that the replacement is a 12V 21/5W bulb because the wrong bulb will also cause the EPC to trigger also without leaving a DTC.  A faulty brake-light switch (DPST) is also commonly known for triggering the EPC light and sometimes causes the 10A fuse to blow. 

So, when the brake is applied and the switch throws, its contacts reverse, meaning the normally-open contact closes and the normally-closed contact, open. If there is a delay in the switching time, even as short as .5 of a second, the EPC light will trigger, without leaving a DTC.  A tell-tale sign that the brake-light switch is faulty or that the fuse is blown; is that the Cruise Control appears to be faulty. Since they are both interconnected, the Cruise Control is reliant on a voltage provided through the brake switch. 

DTC can often be intermittent or sporadic so it’s best to ignore those, in preference of repairing those that are permanent. In so doing, they may have interrelations and the sporadic ones may disappear after the permanent errors are fixed. So, it’s best to perform a diagnostic scan, preferably an autoscan with VCDS first, then delete all DTC in the process. Thereafter save this scan and printout a hardcopy to store with the vehicles registration papers. 

The importance of this printout is that it’s a reference to all the modules coding, and if something is inadvertently changed, there would be an unalterable record to refer to. Once done, and as mentioned above, disconnect the battery's negative terminal then disconnect the positive pole and place the battery on charge for about two hour.  Replace the battery by first connecting the positive pole then lastly the negative pole.

 By following this sequence you will prevent damage to the electronics modules strew throughout the car.  At this point, all pre-learnt and all stored values would have been erased from the ECU. Essentially all the control modules would have been completely reset, restarting with a clean slate.  After starting the engine and driving the car for a short distance, check to see if any DTC have been flagged.

Resetting an ECU occasionally is a good thing, because any and all electronic equipment with a microprocessor can experience an unrecoverable error or an internal parity error or fail a cyclic redundancy check and requires a "cold" system restart. Computer  memory (RAM) also experience memory read/write errors, interrupt or address errors and general protection errors; so  when the ECU is reset/cleared, along with its non-volatile memory, the memory (RAM) is also reset.  AUOTSAR and its core partners are trying their utmost to rectify such problems in automotive ECU, but until they do, we will have to contend with EPC problems.

To read the first part... click here.

The definitive EPC guide

The Definitive EPC Guide

The following is the definitive guide to the Electronic Power Control (EPC), but before we continue, let me expound on what this guide is and what it's not. The very purpose of a guide is to provide information; to aid, give direction, to grant assistance, to facilitate, to support and to help you towards a solution or provide you with an explanation or an answer. However, even though this guide may furnish you with several answers, not every question can be satisfied by the same answers, though it could possibly steer you in the right direction. Hopefully you'll find this EPC guide definitive enough to provide you with the necessary knowledge to fix your Volkswagen, Audi, Seat or Skoda's EPC problem. Or at the very least, steer you in the right direction or share the lingo with which to discuss your EPC problem with your mechanic. 

But before I continue, let me first explain what EPC is. EPC stands for Electronic Power control and is a subsection of the OBDII. OBDII sometimes writen as OBD2 stands for On-Board diagnostics 2, which is composed of mandatory equipment installed in every motor vehicle manufactured since 1996. The purpose of this real time OBDII system is to control harmful exhaust emissions, by rigorously controlling the moment of combustion as close to the Stoichiometric  ideal as possible. Stoichiometric combustion is therefore controlled by an ECU (Electronic Computer Unit) in conjunction with the mass air flow components and the lambda oxygen sensors through constant feed-back in order to increases or decrease the short term fuel trim.  

To define an ECU instance, one could say that it consists of one microcontroller with its peripheral chips and its configured  software application.  This also implies that if more than one microcontroller in packaged in the same ECU housing, each microcontroller requires its own description of said instance. As such, each ECU forms an integral part of the OBD2 system, with strong interaction between hardware sensors and actuators; constantly monitoring and controlling several other engine components to provide the best engine performance at the most efficient fuel use , as well as provide the driver with the best driving experience. Another part of the OBD2 system is its network bus which interconnects several distributed computerized modules, ECUs, sensors and actuators, collectively geared towards better functionality and passenger safety. But before I get carried away, let me return to EPC.

The EPC sub circuit when triggered turns on the EPC light or LED which displays the letters EPC quite brightly in the display console. Many VAG car owners have asked “What's the meaning of EPC warning light when it comes on in a Volkswagen"? Short answer; it’s just a caution light like any other warning light, drawing your attention to a possible problem but with one exception. This exception is that the EPC light is an amber/yellow light and not red. 

Much like road signs that have different colour boards for danger/warning than for  prohibitory/restrictive signs  or than for  service/information  purposes, the automotive sector uses, red lights to signify danger/warning which warrants immediate attention and amber/yellow lights for informative/attention which also requires your attention, though not immediate. When the ECU detects that the engine oil is low for example, it turns on a red light – red oil-can image – which implies that it's dangerous to drive the car in that condition because its engine could seize and therefore begs you to respond and remedy this situation immediately. 

Likewise when your handbrake in engaged, a red light – red disk with a P or exclamation mark inside –  is displayed, implying that it's dangerous to drive with the handbrake engaged, expecting you to release it immediately. Disregarding this red light and driving the car with the handbrake engaged could cause the brake pads to overheat and fail to function when needed but that’s to say if the car would even move from its stationery position with the brake engaged. Headlights on the other hand are indicated by a green dashboard light or a blue dashboard light when the Brights are switched on, neither implying danger nor attention. So in that sense, the yellow EPC light is just an attention light, much like the yellow safety-belt-light provides information that you haven’t bucked up or the yellow reserve-fuel tank-light informing you that you would have to add fuel shortly.  

Very importantly, a yellow light doesn't mean disregard, because disregarding a fuel tank yellow light could leave you stranded without fuel along the roadside. Or disregarding the yellow seat belt light could result in a traffic fine for non compliance to traffic laws. Therefore do not disregard the yellow EPC light and have the possible problem seen to at your earliest convenience. I hear you asking “What can I do when the Yellow EPC light comes on"? Normally when the EPC light comes on, it is accompanied by "Limp-mode home" and sets a DTC in the ECU non-volatile memory. So you need to have your car scanned with a diagnostic tester to determine and analyse the DTC error. 

I hear you asking "What is limp mode". Short answer, when the ECU detects a problem in the toque circuit it prevents the engine from revving above 2000rpm. In effect, it limits the electronically controlled throttle valve – Drive-by-wire – from opening wider.  “So what’s this Drive-by-wire thing”? you may ask.  Well the drive-by-wire circuit is a sub circuit of the EPC circuit and it simulates an accelerator cable, where the depression of the accelerator pedal is monitored by the ECU which in turns drives the throttle body valve open, in unison with the pedal action without any physical cable connection. Essentially it's an electronic version of an accelerator cable /acceleration process. Its electronic circuit is composed of dual sensors constantly monitored by the ECU, and any interruption in its data, will more-likely-than-not trigger "Limp-mode home", turn on the EPC light and set a DTC.

The ECU also constantly monitors the dual sensors in the throttle body as well as  the motor that drives the throttle body butterfly valve. Any interruption in its data will more-likely-than-not trigger "Limp-mode home", turn on the EPC light and set a DTC. This is a safety feature built into OBD2 to prevent the car from going into runaway mode with the possibility risk of injury. Image what would happen when a frayed accelerator cable jams inside its armoured sleeve, unable to decelerate the engine whilst travelling at a speed in excess of 72kph. Considering more than 50% of all accidents in rural areas happens at speeds between 72kmph and 80kmph whereas 70% of all fatal crashes on the freeway occurs at speed of 100kmph or higher.

Continue to part TWO.... Here!

AUTOSAR and the automotive black box.

AUTOSAR and the automotive black box.

Within the next few days the 11th AUTOSAR Open Conference will be hosted at the Portman Ritz-Carlton in Shanghai China. The date of this event is scheduled for the 6th - 7th November of 2018 and that's a mere 8 days from today. At this conference AUTOSAR experts from within the automotive industry will present their  "Future Automotive System Architecture", both  the  Classic and the Adaptive Platforms. Both specifically developed to support high performance microprocessors, with improvements in the safety and security demands for autonomous driving vehicles, aka self driving vehicles. Essentially all motor vehicles of the future.

AUTOSAR logo

They advocate that, due to the latest connectivity requirements and the enormous possibilities available through the “Internet of Things” it is mandatory to upgrade the current system architecture of automotive electronics. Especially when considering their new applications like advanced driving assistance, electric mobility, autonomous driving, V2X (vehicle-to-everything communication) and off board connectivity over the air (OTA).

So what does all this mean in layman's terms. Well, it is AUTOSAR's attempt towards automotive standardization and for the development of smarter, safer and more secure vehicles in the future.  So, who is AUTOSAR you may ask? The short answer; AUTOSAR stands for (AUTomotive Open System ARchitecture) and is a worldwide development partnership of over 250 vehicle manufacturers, suppliers, service providers and companies from the automotive electronics, semiconductor and software industry. Their collaboration  and  collective objective is to agree on a "Standardized Software Framework for Intelligent Mobility" and implement it, as the way forward. 

An incomplete overview of the AUTOSAR Runtime Environment
and how components plug into it

This would simplify replacement and updates for software and hardware, which essentially forms the foundation for reliably controlling the growing complexity of electronic and software systems in today’s and future vehicles. The AUTOSAR alliance was formed in June of 2003 and comprises of  9 "Core Partners"  viz, BMW Group, Volkswagen Group, Continental, Daimler, Ford, General Motors, the PSA Group and Toyota. In addition there are some 43 Premium members as well as another 112 associate members collectively contributing to the motor industry.

Standardization is a good thing and when coupled to "open architecture" is even better. Case in point, Linux is open source and it revolutionized computing.  Linux was selected for its ability to run on many and various makes and models hardware boards. Besides, Linux more-likely-than-not has the widest device driver support of any other operating system on the planet. As such,  Linux became the de facto application software for developing specialized embedded devices in consumer electronics. For example, personal video recorders (PVRs), wireless access points (WAPs), personal digital assistants (PDAs),  Global positioning systems (GPSs), in-vehicle infotainment (IVI), routers, switches, set-top boxes, navigation systems, home automation systems, car dashboard sytsems, security appliances, etc. 

Linux is such a highly flexible platform that makes it relatively easy to port to other hardware architectures. As such Android relies heavily on its level of hardware abstraction (HAL). Android is an open source Linux-kernel-based operating system which revolutionized handsets far beyond phones, tablets and TV's. When Google acquired Android, they created the Compatibility Test Suite (CTS), which defined what OEM's handsets should comply with, to be Android-compatible.  This CTS is just just a HAL (hardware abstraction layer) for the Android stack. 

In the same vane AUTOSAR intends an open and standardized software architecture for automotive electronic control units (ECUs). It's RTE will act as a HAL sitting on a layer between the application software and the Hardware.  It would form a standard ECU (black-box) usable by all manufactures with a layered software architecture that would reduce individual expenditures for research and development while mastering the growing complexity of automotive electronics. 

The AUTOSAR operating system is also backward compatible with OSEK/VDX (ISO 17356) and consists of Basic Software Modules, Application program Interface (API), Specification of ECU Configuration Parameters (XML), Standardization Template, Generic Structure Template, Interoperability of AUTOSAR Tools.  Hopefully the AUTomotive Open System ARchitecture would do for cars and safety in general what both Linux OS and Android OS have collectively done for consumer electronics as a whole.