EPC Q & A REVISTITED

EPC Q & A REVISTITED

Of late, Vag vehicle owners are experiencing Electronic Power Control problems more frequently than ever before yet most VW, Audi, Skoda and Seat still have no idea what an EPC fault is and what causes the EPC light to turn on. To add insult to injury some VW, Audi, Skoda and Seat service agents tend to "repair" these faults by trial and error, costing the vehicle owners exorbitant amounts of money only to later discover that the fault persists. The EPC warning light can be found in selected models in virtually all makes of cars and is not limited to just Volkswagen Audi, Skoda and Seat vehicles. Volkswagen Audi, Skoda and Seat use Electronic Power Control in their drive by wire vehicles as a safety feature which in my opinion isn't all that safe. Case in point, I have had my VW Polo go into limp mode whilst overtaking a car in a two way street.  It stalled at the very moment when I was cutting-in in front of the said car, causing its driver to frantically brake and swerve to avoid colliding with the rear of my car because  suddenly I wasn't accelerating any longer. Not to mention the on-coming car, which swerved toward the shoulder of the road since my car was straddling the white line. My EPC problem turned out to be the incorrect octane fuel.

Be that as it may, by the time the EPC light illuminates in the dashboard, in response to some sensor detecting a problem, the problem already occurred in either the torque control, traction control, throttle body and sensors, accelerator pedal sensors, cruise control,  fuel supply or ignition systems. Essentially the epc light is just a way to tell you that there is a problem with the drive by wire system and generally remain on until the fault is cleared.  At the instant that the EPC light illuminates, the  ECU flags a DTC which is then stored in the relevant electronic control module. This DTC gives a fair idea of the suspect system but cannot pinpoint  the culprit component. 

QUESTION?

Anonymous says:- Hey I have a 06 Passat 2.0t and I am reading all of these stories on the EPC my check engine light was already on while I was driving but the car was good. I was on my way to work after stopping at the gas station and my EPC light came on and my car stalled on the highway and has not came back on. The lights windows and everything works but when I try to turn the car on it attempts to turn but never does. 

ANSWER!

From your description I understand that after your EPC light came on, your car won't restart. So you checked the light and windows which tells me you suspected that the battery may have run down and perhaps not strong enough to turn the engine over.  But you also mentioning 'check engine light'. A combination of check engine light and EPC light is emissions related and if your car's emissions exceed a predetermined level, the ECU will prevent the engine from starting. Its best that you have your car scanned to see what DTC it threw out. 

QUESTION?

Musa Brain says:- Hi there. I have a VW polo vivo I have the EPC light on when I'm driving slowly and also when I'm reaching a stop sign and hit the clutch pedal it turns off and when I start it in the morning it turns off so I have to rev it for it to idle but after some few minutes the EPC light comes on. Please help?

ANSWER!

Musa your description of your EPC problem seems that you car doesn't idle fast enough. I assume that its drives normal whiles on a higher rev. It quite evident that it switches off when you come to a halt and whilst it's cold. I suspect that you have a blocked air filter problem that doesn't allow sufficient air to the MAF, but I could be wrong since you provide no DTC's. It could also be a blocked fuel filter that starves stichiometricity since torque is determined by both  air and fuel. 

QUESTION?

Bogdan Iova says:- When I swich key on the EPC light not apear and teh engine not start. Golf 1.6 16V 

ANSWER!

Bogdan, you really haven't given me much to work with here, but off hand it seems that you may have a blown fuse that powers the instrument cluster. Because the moment you turn on the ignition key, the OBD II system does a self  diagnosis by turning on all the dash board lights for about 10 seconds whilst running the test.  It then turns off  those light related to the circuits that function normally and leaves those lights on, for circuits that fail the test.  So, if you EPC light does come on when you turn on the ignition , then goes off,  you don't have an EPC problem.   However if your engine won't start it's obviously cause by something else. It could be that your battery has reached end of life. If the engine doesn't turn over, even the starter could have packed-up. But if it does crank and won't start, check your fuel gauge to at least determine that you have fuel in the tank.  Related to this could be your ECM Power Relay, your fuel pump relay or the fuel pump itself. Without more info, this is about all I can help you with. DTC codes would have been helpful.

QUESTION?

Anonymous says:- Hi there, I have a 2003 polo 1.6, EPC light is on and when it's idling can't rev it, checked and cleaned the throttle body and still same issue, ran a diagnostics check and it says something about the pedal, please help?  

ANSWER!

Hi Anonymous, you seem to have a classic EPC problem but for the benefit of everyone else, it would have been great to share the DTC codes that you recovered. I suspect it must have been one of the following codes since you mention the error code said something about the accelerator pedal.

18038  P1630 Accel, Pedal Position -G79 signal too small  (low)
18039  P1631 Accel, Pedal Position -G79 signal too largely (high)
18040  P1632 Accel, Pedal Position -G79 supply voltage  malfunction

18041  P1633 Accel, Pedal Position -G185 signal too small
18042  P1634 Accel, Pedal Position -G185 signal too largely
18047  P1639 Accel, Pedal Position -G79 & -G185 out of range 

You also mentioned that you checked and cleaned the throttle body. If you dismantled it in anyway, then you need to redo adaptation, else the ECU would have no idea how wide the butterfly valve has opened.  Remember there is no throttle cable connecting the accelerator pedal to the throttle housing. This is known as a drive by wire system and it communicates the driver's torque demand to the ECU. The two potentiometers in the accelerator pedal assembly communicates the pedal position directly to the engine control module (ECM) using two separate signals, one signaling the pedal physical position and the other indicating rate of pedal movement.  You will need a scan tool to do the adaptation because any faults in memory must be cleared before adaptation can be done. 

The most common problem is the accelerator pedal itself. One or both of the potentiometers go high resistive/ intermittent and the accelerator pedal assembly should be replaced as a single unit. A tell tail sign of accelerator pedal trouble is that the engine revs higher than 800 rpm and at times the rev counter rises and falls continually whist idling, going as as high as 2000  rpm. If this happens, grab hold of the pedal whilst the car is idling and pull the pedal upwards, away from the floor. If the revs reduce and the surging stabilizers, replace the pedal. The image above shows idling whilst engine in surging and  the image below shows idling with the pedal pulled up.

DOOR LOCK PROBLEM ON POLO 9N

DOOR LOCK PROBLEM ON POLO 9N

For the past week or so, I've noticed some peculiarity  with my VW Polo's left side  front passenger door locking mechanism. To risk stating the obvious, my VW Polo is a right hand drive car. Its auto lock feature is enabled, so when I drive and reach about 15 kmph all the doors lock simultaneously and the sound made by the four solenoids are clearly audible when this happens. But then, the front passenger door immediately unlocks itself. Initially it was the sound of the solenoid in the left passenger door that alerted me to the fact that it locks then unlocks itself.  

Physically, all four door buttons/knobs  are retracted at 15 kmph, three stays down but the left front passenger door buttons/knobs pops back up again. After this happened a few times,  I re-locked it  by pressing the internal central locking button on the driver's door panel. The left passenger door responded to the central locking lock instruction by re-locking but then immediately unlocks itself again. It just doesn't seem to want to stay down.

Thinking that it was just an electronic glitch and that the door might still be locked, even if the button jumps up. So I stopped the car, rolled down the left passenger window, climbed over the console, stuck my hand outside and pulled on the door catch. Surprise, surprise the door opened.  So I thought to myself, this isn't good, in fact it really sucks.  It's a huge safety risk driving with an unlocked door, especially considering the amount of bag snatching and car hijacking that's been taking place of late. 

Thieves and criminals hanging out at stop signs and at a traffic lights patiently await the opportunity of an unlocked door coming their way, so that they can jump into your vehicle and rob you. I know of a case when three villains jumped into a nurse's car and forced her at knife point to drive to an ATM, to withdraw her daily cash limit. They then held her hostage until after 12:00 the evening just so that they could get the balance of her money from her account which was less than her daily limit for the next day. Fortunately they didn't harm her, but her nerves were totally shattered.   Anyway, what I discovered much late is that when the passenger door button/knob pops up and I can manually press it down, and it doesn't pop up thereafter and the door stays locked.

Anyway, this door button/knob popping-up  started to irk me and it was getting flippen irritating, so one afternoon when I got home from work, I decided to tackle the problem. I switched off the engine, removed the key from the ignition, and all the doors unlocked simultaneously, which is absolutely normal.  So I re-locked the car with the fob remote key and all the buttons stayed down as they should. When I depressed the fob remote key unlock-button twice in quick succession, and all the doors unlocked which is also perfectly normal. From this I deduced that the electronic circuit responsible for unlocking the passenger door must get its power via the ignition switch, since it only unlocks when driving at 15 kmph and not whiles it's stationary and therefore  there has to be a dedicated switch in each door. 

But before I start taking things apart I needed to make absolutely sure that the problem is in the left front passenger door.  I once again used the fob remote key to lock  all the doors to make sure that they stayed locked, which they did. When I unlocked the Polo with the fob remote key, only the driver's door unlocks which is perfectly normal. But within 3 seconds the left passenger door also unlocks, and that's not normal. So I realized the problem is specific to the left passenger door yet I needed to make absolutely sure.

Sitting in the drivers seat, I  turned on the ignition and opened the drivers door and saw the  red light, door-open icon in the dashboard instrument cluster turn on. I repeated this process on the front passenger and rear doors, as well as the boot lid, all of which activated  the red door-open icon except the left front passenger door. The next test was observing the interior light. As I opened the driver's door to get in, the interior light turned on, so I waited for the light to automatically turn off. I then reopened the door and the light turned on as it should. I repeated this action on the other doors which also worked as they should, except the front passenger door that didn't register that it was opened because the interior light stayed off.  

From this I deduced that both  the instrument cluster door-open icon and the interior light is powered from the same switch in the door which is actually  intermittent when not short circuit. Then I got out my laptop and my VCDS cable, rigged it up and Voila! With the all the doors wide open, as can be seen in the image below, the passenger door switch remained closed.

As can be seen in the above image, with all four doors open, the  software
still sees the passenger door is closed

As can be seen in these images the door and trunk Measuring Value Blocks are 005, 006 and 007. With all the doors closed, as can be seen in the images below,  the state of the passenger door switch didn't changes at all. So just for the hell of it, I banged the passenger door a few times hoping that the switch would budge because I'm certain it was stuck in place rather than the contacts burnt together. 

Now that the preliminaries are out of the way,  I can finally get out the screw drivers, spanners and the torx wrench and dismantle that pesky door mechanism. The following pics gives a fairly good idea of what it entails to remove the door lock; and on a scale of 1 to 10 with 10 being the most difficult I give it a 7. Removing and replacing the steel trace link that fits between the exterior handle and the lock is quite a challenge if you  have large hands. 

The door panel before dismantling it

The plastic cover removed to expose the screws.

Removing door handle screw with hex key

The inside view of the door panel with the electric window plug unplugged

The slide mechanism mounting plate with all its screws removed

Removing the torx screws that secure the door lock

The sliding window removed from its clamps and stored safely

Screws of the backing pate, the inside door handle, 
the door lock and the inside door lever

The passenger door lock with the micro switch dangling on its blue and red wires

I sprayed the the micro switch with some Q20 multipurpose lubricant  and flicked it a number of times. I also cleaned the the metal pawl that activates the micro switch. It has a little notch in it, that fills up with grime. I suspect it is this grime and plastic burrs that cause the micro switch to misbehave.  I used two straight pins to pierce the insulation of the micro switch wires in order to connect my Fluke multi-meter so that I could do a continuity tests.

Continuity measurement of the micro switch in its normally open position 

Continuity measurement with the micro switch depressed -closed position.

The steel trace link between  the outside door handle and the lock.  It is 
quite difficult to remove and put back especially if you have large hands.

The door lock "question mark looking" lever, is where the 
short steel trace cable links into

The steel trace must be held in the horizontal  position before it can 
be inserted  into place.

Showing the steel trace link in place, but it has to inserted during 
assembly when the lock in secured to  the door frame.

Several other VW Polo owners have had similar problems with one or more of their doors. For example: When you lock the car with the inside central locking button, the left hand side passenger door does not open when it is unlocked, so the driver has to roll down the window an open it from the outside. I clearly remember that both my Golf 1 and Golf 2 had door lock issues and a replacement lock was really cheap. In fact it was less that the price as a pack of 30 cigarettes. But times have changes and considering the replacement cost of a VW Polo door mechanism (R900 -R1200 excluding labour) and what a shitty job it is to replace it, most drivers just learn  to live with it.  The nature of VW central locking issue can range  from mechanical to electronic, from a sticky micro switch, to cracked/dry solder joints on the printed circuit board. Sometimes  grime / builds -up between the micro switch and its activator, so give it a good clean and spraying the micro switch would be wise once the relevant lock has been removed. 

I know of a VW Pasat that had a similar issues. When the car is unlocked with the fob key neither of the inside nor the outside handles would open the door and since the door needs to be open to repair/ remove  the lock, the car eventually had to go to the agents who charge a whopping R5500.00 to fix it. At least if the other doors had a keyhole to open them, it would have been so much easier. But it is all about cost saving for manufacturers.

Other issues

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