Thursday, November 9, 2017

Check Engine Light

Check Engine Light - aka MIL

Yesterday morning when I started my VW Polo highline she idled a bit rough but I never gave it another thought because it had been raining hard throughout the night with harsh howling winds accompanied by a  lightning storm. I summized it could have been caused by the moisture in the air but when I looked at the dashboard, I saw that the orange / amber Check Engine Light was on. I tried accelerating and looked at the CEL but it stayed on. Surprisingly the engine seemed sluggish and didn't revv as per normal. Looking through the rear view mirror, I could see a distinct amount of smoke spiraling behind the car.  This was worrying because the previous day,  the car drove perfectly normal and when I parked her, she idled just fine. 

The problem with the  Check Engine light, other that being on, is that it doesn't tell you anything about the nature of the problem nor whether it's  serious or not. All I knew is that something was wrong with my emission control system because of the excessive  smoke.   The Check Engine light is actually better known as the Malfunction Indicator Lamp (MIL) so in essence there was a malfunction detected by the ECU and there was no way to tell what it could be without plugging in my scan tool. So off I went and  fetched my laptop and my VCDS cable, plugged it into the under dash DLC connector and ran a scan and found 4 Faults - P1137, P1103, P1187, and a P0441.

CODE ERRORS

17545 - Fuel Trim: Bank 1 (Add)
P1137 - 002 - System too Rich - MIL ON

Considering the first error code describes the fuel system as to rich, by implication then there is too little air for proper combustion. So I popped the bonnet to check the MAF, and saw a whole load of leaves and pine nettles strewn all over the engine compartment and a hand full of them stuck to the inlet of the air filter, blocking the air flow. I then open the air filter, removed the leaves and nettles and all those that got sucked into the air filter housing when I initially started the car.

17595 - Linear O2 Sensor; Compensation Resistor: Open Circuit
P1187 -- 35-10 - - - Intermittent

The second error directed me to the O2 sensor because the ECU describes it as  "Open Circuit".  Stooping over the engine, my eye followed the exhaust pipe, from the manifold branch past the firewall and saw a pine tree branch under the car, so I kneeled down to pulled it out but is was stuck. The tree branch was right below the  Catalytic converter.  I then went inside to fetch a garden pruning scissors so that I could cut off the protruding twigs and free the branch. Just as I was cutting I saw a wire hanging from down from the Cat. It was the wire from the O2 sensor that broke off and I supposed this happened with the force of the wind blowing the branch under my Polo.

The road and my driveway was littered with pine comes and nettles that the wind blew from the park more than a 100 meters away.  Anyway, I striped of the O2 sensor wires which was screened and reconnected them with an electrical block connector. You know the ones were you have to push the wires into a brass ferrule from either end and screw it down with the two screws. That just worked perfectly.

17511 - Oxygen (Lambda) Sensor Heating; B1 S1: Performance too Low
P1103 - 35-10 - - - Intermittent

The third error also directed me to the O2 sensor that wasn't heating up. I suppose it's linked to the disconnected wire and I assume the ECU prevented this because it realized the O2 sensor was OC. 

16825 - EVAP Emission Control Sys: Incorrect Flow
P0441 - 35-10 - - - Intermittent

The fourth error I couldn't make sense of  though I've seen this error when the fuel tank cap wasn't properly closed. So I went to the the tank, took off the cap and inspected the rubber seal. But it all seemed fine, so I closed it. I them cleared the diagnostic trouble codes (DTC) stored in the engine control module and started and re-scanned the ECU for errors and it came back with "No fault code found ". I then started my Polo and all was well. She revved as before and the Check Engine light was off.


The Check Engine light has always been a major annoyance to both motorists and mechanics,  and as a consequence is often ignored. I even know of someone  who stuck a piece of black insulation tape over the orange / amber  Check Engine light to blot it out, rather than fix the problem. Be that as it may,  ignoring the Check Engine light could lead to expensive car trouble later, so it's important to promptly address problems indicated by it.

DIY mechanics should buy and inexpensive scan tool / DTC code reader  since they are all standardized to plug into the 16 pin DLC under the dashboard. It would empower them to  discuss the problem with their mechanic if they can't manage to solve it themselves. When Check Engine light comes on, it is more likely than not that your car car is releasing unburnt gasoline (hydrocarbons) and carbon monoxide  into the atmosphere and consume a lot more fuel than it actually should.  

The OBDII system was primarily designed to monitor the emission control system continuously so it can be said hat if you car passes "readiness" its a good indication that your car  engine is in good health.  

Some problems that can illuminate the Check engine Light.

A clogged air filter can trigger the Check Engine light.
A loose gas cap can trigger the Check Engine light.
A fault O2 sensor can trigger the Check Engine light.
A Mass air flow sensor problem can trigger the Check Engine light.
Perished Spark plug wires can trigger the Check Engine light.
A blown  Catalytic converter can trigger the Check Engine light.
Low oil pressure or overheating can trigger the Check Engine light.
Sporadic engine misfiring can trigger the Check Engine light.

  

Tuesday, November 7, 2017

Hall Sensors

VW POLO

Volkswagen has always had an upstanding reputation (other than for the emission scandal) for manufacturing quality vehicles at affordable prices. One such car is the VW Polo hatchback which has also become one of the most popular cars in South Africa, and it’s really not hard to see why. The VW Polo is a compact car, but when driving it, it somehow feels larger, somewhat like its bigger brother - VW Golf. Should you buy one, you would certainly agree that the VW Polo has universal design appeal, that it has good performance, decent fuel economy and is sold at a relatively affordable price. 

Hall Sensor Hall Effect Sensor Switches A3144 / 3144E / OH3144E
in a TO-92UA 3 pin SIP package can be bought for as little as 1 USD
Volkswagen has capitalize on this winning formula for years and has given us plethora of Polo's to choose from ranging from the Polo Trendline, to the Polo Comfortline, to the Polo Highline, not forgetting the Polo Cross and Polo GTI which comes in 3 and 5 doors classic and hatchback versions. Engine capacities and engine technologies range from 1.2 TSI 66kW and 1.4 TDI 55 kW for the Trendline,   1.4 TDI 77 kW, 1.2 TSI 81kW for the Highline  and 1.2 TSI 81kW Highline DSG, to  1.0 TSI 70 kW BlueMotion. The sedan or VW Polo Classic comes in  1.4 & 1.6 trendline, 1.6 comfortline / tiptronic, 1.9 tdi highline (74kw)  and 2.0 highline (85kW).  There is even a GTI (Grand Touring Injection), a FSI (Fuel Stratified Injection), TSI (Turbo Stratified Injection) and a TDI (Turbocharged Direct Injection), to choose from. 

Clearly there's a Polo out there waiting for you! Having said that, owning a Volkswagen doesn't come without challenges, personally I think the biggest challenge is more likely than not the dreaded EPC light that triggers at the most inopportune times. The EPC circuit has several sensors that feeds into the ECU among them Hall sensors. From my experience hall sensors tend not to like heat, even though their specification sheets rates them above the requisite heat range.  
This datasheet gives you a good idea of a hall sensor's specifications 


Hall sensors are pervasive throughout modern day cars. Hall sensor, aka Magnetic sensors essentially converts magnetic pulses into electrical input signals for processing by electronic circuits. Magnetic sensors are solid state devices meaning there are no mechanical moving parts inside, its all electronics taking place in a sealed chip of silicon, making them immune to vibration, dust and water. This makes them popular choice by electronics designer engineers for several types of application ranging from  distance sensing, to velocity sensing, to position sensing, to  speed sensing, to directional movement sensing etc.

Hall sensors are used for angular position sensing of the crankshaft to determine the firing angle of the spark plugs. They are used for magnetic position sensing in EGR systems. They are used for wheel speed detection for the anti-lock braking system - (ABS) and speedometer. Throttle bodies with DC motors use hall sensors for position sensing. Hall sensors are also used to determine the position of the car seats and locking of seat belts. Hall sensors are employed in automatic transmissions as magnetic neutral position switch, as actuator sensors, as speed and direction sensors, for gear detection and clutch position sensing. Hall sensors are used as engine speed sensor and also as the vehicle speed sensors.  And the list goes on.

The following images depicts a hall sensor replacement inside the distributor of and Audi 5-cylinder engines 2.0 - 2.3. As can be seen the the wires have distinct colours , the red wire is +5V / 12V supply, the black wire is negative / ground and the yellow wire is the output of the hall sensor / sender.

There is space under the black plastic holder where the wires connect to the hall sensor.

Multi purpose hall sensor for automotive use, but the military spec hall sensor is a better option
The sensor is replaced, solder joints covered with fiber glass sleeving then epoxied into place.
Hall sensor plate reassembled
Hall sensor assembly fitted into distributor housing

As I mentioned in a previous blog, Hall sensors don't like heat and tend to malfunction when they get too hot. My first experience with hall sensors were when I was working as an electronics engineer for A Television and Video repair company. A video machines that employed a hall sensor in its take up clutch stopped working due to overheating.  By squirting the hall sensor with a blast of servisol rapid cooling spray, it started working again. I repeated this exercise a few times to make certain that the hall sensor was the culprit, after replacing it, the machine worked just fine. 

Then I also had a problem with my Opel Kadett 1.8 GSI  when driving in peak hour traffic. It would switched off and refused to start.  But after allowing the engine to cool, it started just fine and would be perfectly ok for days until I got stuck in bumper to bumper peak hour traffic again. The dealer had a field day with my car, telling me that they repaired a bad earth under the dash board, only to find out in peak hour traffic that they misdiagnosed. Then I was told that the loom was replaced, then I was told the ECU was replaced and finally that a hall sensor inside the distributor was replaced. This fix the problem once and for all. The images above is for the same symptoms on a Audi  2.0L 5 cylinder.  As perfect as hall sensors are for most applications, where there is excessive heat, they will misbehave.  Perhaps hall sensors mounted in heat intensive spots like the engine speed sensor, should be designed with a heatsink or have its own cooling fan. This advice is as relevant for current model cars as it was for the Audi 2.0L 5 cylinder.

Sunday, November 5, 2017

Volkswagen Polo

Volkswagen Polo

The Volkswagen Polo Vivo is undoubtedlty the most popular, as well as the  best-selling car is South Africa. Looking at the top ten vehicles sold in South Africa, VW Polo Vivo takes first place, the Volkswagen Polo takes third place and the Vw Golf takes tenth place. Looking at the frequency of problems encountered with Volkswagen vehicles  in general, it appears that the VW Polo 2002-2009 models are far more reliable than the VW Polo 2010—2016 models. These models are prone to EPC problems and several Polo owners have complained that they encountered EPC problem with their cars with as little as 700km on their clocks.

The most troublesome generation 5, VW Polo seem to be the 2011 model, but the 2012 model takes the cake for the annoying knocking sounds coming from the suspension when going over speed bumps and pot holes.  But this knocking sound isn't unique to the Polo 2011 and 2012 models, it also affects the Golf Mark 7, the Volkswagen Transporter T5 and Polo GTI, etc.




It seems that somehow the strut mount bolts in the engine bay of these Volkswagens haven't been torqued properly. The rattling and knocking noise coming from the shocks occurs when driving over pot holes  or over speed humps, especially when the shock is fully extended or when driving slow.  In some cases the noise comes from coil-over assembly. These coil-overs squeek and creak at random and sometimes the rear ones squeak worse than the front ones. We found by removing the damper adjustment knob and tightening the 17 mm nut in the middle of your strut top,  and   holding the centre with a 7 mm allen key,  the noise is  somewhat reduced but is very disconcerting since these models are relatively new cars. 


Its probably best to re-torque these nut between 45-60 ft/lbs with a correctly  calibrated torque wrench. In my opinion there should have been a total recall on VW Polo 2010—2016 models for this problem. 

Saturday, November 4, 2017

Loss of Power

LOSS OF POWER

On Sunday past, whilst taking my family for a drive along our scenic coastline on the Western Cape, I happened to see no less than three Volkswagen cars, each being loaded onto a roll-back. A VW Polo Vivo in Muizenberg, an Audi S4 in  Fish Hoek and a VW Scirocco in Scarborough. I couldn't help but feel awkward about my own Volkswagen Polo because after all, three out of three vehicles on the roll-backs were Volkswagen manufactured cars. I would have felt loads better if at least one of them were a Toyota or a Ford or a Honda. Understandable there are a lot more Volkswagen vehicles on the road than any other make, hence the higher failure rate.  

However, I instinctively pulled over for a chat with the driver of the Scirocco to inquire about the problem. It's owner Gwendaline. apparently parked her car to go for a walk on the beach and when she returned, had difficulty in starting her car. When it finally started , the whole car shook like her washing machine does in its spins cycle.  According to her, the Scirocco  is  really an excellent car with very few issues other than regular EPC light issues; and that its 18 inches tyres are a bit expensive. So we started talking about the EPC - Electronic Power Control and she seems really knowlegeable about it.  Our conversation went something like this.

Electronic Power Control

The EPC warning light, is just an indicator light powered by the Electronic Power Control circuit. Most people are under the impression that it indicates that there is something wrong with the engine when it light up. But this is not exactly the case, because the EPC light does come on when a brake light is fused or the fuel tank cap isn't properly closed.  When The EPC warning light flashes or stays on, it merely alerts the driver to a problem that may exists in your Volkswagen's throttle system. The throttle system encompasses  the throttle body, the throttle control motor, the accelerator pedal, the drive-by-wire electronics, the traction control, the cruise control, the stability control, the fuel delivery system and even the braking system and all their sensors, etc.. 


What does it mean when the EPC warning light turns on in a Volkswagen?

The throttle body motor opens and closes the butterfly valve located on the intake manifold which regulates the amount of air that goes into the engine, in relation to the position of the accelerator pedal. Implying the higher the air flow into the engine, the more fuel the ECU injects, thereby increasing  or decreasing the power output of the engine. When a problem is detected in the throttle system, a signal from one of the sensors triggers the  ECU into illuminating  the EPC  warning light. 


The Electronic Power Control (EPC) is just a part of the Engine Management System, which in turn is part of the overall On-Board Diagnostic II system. Normally when the a problem is detected that causes the EPC light to turns on, it also sends fault codes to the dashboard module or gateway module, vehicle model dependent. These fault codes can be retrieved by an ODBII scanner / smart phone, which are key to isolating the area of the throttle system that has failed. Most EPC light and ESP light problems will limit your Volkswagen's output power, commonly known as "limp mode".  

It is advisable that when either the EPC or ESP lights turn on, the problem associated with it be repaired timeously. A Volkswagen in limp mode should not be used to run errands, and since the car has sufficient power to drive it to  dealership or mechanical repair shop, it is best to do so. Normally once the fault / problem is remedied the EPC or ESP light will turn off. However, there are hundreds if not thousands of Volkswagen owners who have taken their Volkswagen cars into dealerships for repair, only to encounter the same EPC / ESP problem a day or two later.  Some of them suffer with EPC problems for months and I personally know of someone who had an EPC problem for more than a year. That's enough to drive the sanest person nuts.


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My W Polo classic 2003 model's EPC light is on and there's no acceleration. My VW Jetta's dashboard displays the word  EPC, now it has no power. My VW Golf diplay the letters Epc, what can I do?  My VW Golf IV cluster shows both epc and esp and it won't revv up, nor go more than 70 km/h. My VW Sirocco 2017 model's epc light has come on again. My car's EPC light is on and I don't know what to do?