DIAGNOSING EPC LIGHT PROBLEMS

DIAGNOSING EPC LIGHT PROBLEMS

VW Polo EPC light goes on and the car won't rev. Audi MIL and EPC light turn on and car goes into lip mode. SEAT suddenly has no acceleration yet has maximum of 1200 RPM. SKODA accelerator problem, won't rev. Audi EPC light on and transmission is locked in park.

Audi and VW crankshaft position sensors.

Question?

Hello mate...
My car was running really sweet when suddenly I'm having throttle issues! I was going to my girls house when all of a sudden, smack bang in the middle of the road, I have no acceleration. The car just cut the revs into idle and causing the EPC light on the dashboard to light up. I managed to get it off the road out of the traffic. Several attempts later to get her to rev up but  nope, absolutely nothing. So I phoned the towing service and the dude  checked under the bonnet to make sure everything was in place so he disconnected the battery for a while so it would reset the computer. It still wouldn't rev, so he hauled it onto the truck and brought it to my house. My neighbour Freddy has a VCDS which he plugged in and these fault codes showed up. I'm desperately in need of help because I have no idea how  to  solve this problem?

Chassis Type: 6K - Seat Ibiza/Cordoba
Scan: 01 02 03 08 15 17 25 45 56
Mileage: 97850km/60801miles
-------------------------------------------------------------------------------
Address 01: Engine

Part No: 6K0 906 032
Component: 1.8L R4/20VT SEA 0002
Coding: 11500
Shop #: WSC 78904

5 Faults Found:

18047 - Accelerator Position Sensor 1/2 (G79/G185): Implausible Signal
P1639 - 35-00 - -
18039 - Accelerator Position Sensor (G79): Signal too High
P1631 - 35-00 - -
18042 - Accelerator Position Sensor 2 (G185): Signal too High
P1634 - 35-00 - -
17950 - Angle Sensor 1 for Throttle Actuator (G187): Implausible Signal
P1542 - 35-10 - - - Intermittent
17581 - Angle Sensor 2 for Throttle Actuator (G188) Signal too High
P1173 - 35-10 - - - Intermittent

Answer!

Hay George.This is quite interesting that both your accelerator potentiometers and both your throttle body potentiometers are acting up at the same time. Normally I would say that your accelerator pedal needs to be replaced if only G79/G185 flags repeated DTCs. Alternatively say that your throttle body needs  cleaning and adaptation if G187/G188 flags repeated DTCs. But this is certainly not the case though both these circuits are notorious for "No Throttle Response", limp mode and turning on the EPC light.  However to me it looks more like the voltage supply line to both devices is acting up, that it's intermittent.  Since the throttle and the accelerator are each connected directly to the same control module (ECU) I'm tempted to say that the ECU plug is probably loose or corroded or the fuse holder that supplies the ECU with terminal 30 (12V unswitched) and the relay that supplies terminal  15 (12V switched) needs to be checked for proper contact and corrosion. What I am willing to say is that you have a wiring harness problem, so check continuity between the ECU and the accelerator pedal 6 pin plug and the ECU and the Throttle body 6 pin plug. Make certain to do adaptation afterwards and check throttle valve control in group  060“ (G187/G188),  and especially 62 (G187/G188 & G79/G185), and 63 (Kick-down) and if you have a cruise control group 66 as well.

Question?

I'm Renshaw and I have an Audi A4 1.8T. When I started my car from cold, the EPC light came on and the engine just stalled. Made a couple more attempts to start but engine just cranks and  wouldn't start. After a while I tried  again and it started just fine and it drove fine. The following day  I couldn't start the engine again. So like before I waited a while and it started fine and I drove all week without any EPC problems, until this morning while standing in peak hour traffic my car just died.  After a few tries the car finally started but while I was driving both the EPC and the MIL (check engine light) came on, the engine lost power and was idling at 1200 RPM. This happened a few time over the past month and I'm really loosing my patient with my Audi A4.  So when it happened again I limped to the service agents  who got the 2 DTC errors:  P0321 Ignition/Distributor Engine Speed Input Circuit Range/Performance and P0322 Ignition/Distributor Engine Speed Input Circuit No Signal, but they could get the car to switch off like it did with me. Something like the toothache goes away when you get to the dentist. Anyway, I've search the Internet forums for a  EPC problem similar to mine but found nothing. I still don't have any idea what's going on. Can you please help me and I would be very appreciative and thank you.

Answer!

Hi Renshaw, thanks for your question. The problem you describing is fairly common on Audi which normally flags any or all of the following DTCs - P0320, P0321, P0322 and  P0323  at the same time. This is undoubtedly or rather more often than not caused by your Engine Speed (RPM) sensor signal (crankshaft sensor) that is out of phase. Bear in mind that your car has a DIS and not a mechanical distributor which is normally driven by a gear on the camshaft. This implies that your camshaft / crankshaft have embedded  magnets that energizes  a hall sensor (crankshaft sensor) or an inductive sensor mounted on the cylinder block which  measures crankshaft speed (interval), that provides the engine speed signal to the ECU. It also doubles-up as the signal that determines the time and duration of the ignition (spark) as well as injector timing. Depending on the model, the crankshaft sensor is next to the oil filter. Crankshaft position sensor (G28) failure is also common on the new VW Polo the new Jetta. 

NB!
If you need help with your EPC problem or an explanation of your diagnostic scan and willing to share the findings with fellow Vag owners, feel free to link to this post and upload  your question and a scan of your car. Not every problem can be dealt since there are a fair amount of overlap / common problems, but I will try my very best to answer as many as possible.

EPC HELP

EPC HELP Q & A

VW Beetle EPC problems. Audi EPC light, Audi Q7, Audi TT, car trouble, DTC, drive by wire, DTC memory, EPC, EPC dashboard light, EPC faults, EPC problem, accelerator pedal adaptation, Audi EPC Light problem, Audi Q7, audi TT, car trouble, crankshaft position sensor, drive by wire, dtc, DTC memory, EPC, EPC dashboard light, EPC faults, EPC problem, high pressure fuel pump, Limp Mode, throttle body, VW Beetle, wiring harness, O2 sensor,

Question?

My name is Lilian. I bought a 2001 Volkswagen Beetle a few months back. Now it loses power whenever that EPC light and check engine light switches on. Lately it happens more  often, so I switch it off and after a while start it again and it drives ok for only a few miles. I just cant go on like this, its upsetting to the point that I can cry. The VW Beetle club members say its the throttle body, so my friend replaced it for me.  It was really expensive from the agents so a got a used one from the junk yard. It fixed the problem, or rather so I thought because after about 200 miles the problem is starting again. Now I feel helpless. Pleeeez help me. Pleez Pleeez Pleez!

Answer!

Hi Lil sorry to hear about your troubles. As much as I would like to help you, you gave me way too little information to steer you in the right direction. A diagnostic scan of the VW would have really been helpful but since you don't have one, fixing it is going to mere guess work. EPC faults, can be solved by a process of elimination and since you replaced the throttle body and it lasted for 200 miles, without a problem, it is very likely that it was the throttle body that was faulty but the question is, did your friend do the adaptation so that the ECU can properly interface and control it? Sounds like this is your problem. You need to take it to a diagnostics equipt workshop to have the throttle body adaptation reset. I'm almost certain that would solve your problem.

______________________________________

Question?

Me Zoe, I got Vw beetle, make power loss and make  EPC dashboard light on. I read  VW forum say was cause by brake light switch. I take my mechanic, he  say no fix, take  VW agents they recall VW Beetles with brake light switch problem. Me very lucky, VW agent replace it free but EPC problem no fix and now more worse. Happen every day. You me help. I you kiss.

 Answer!

Hello Zoe thank you, I am flattered that you want to kiss me. I have to tell you though, that the brake light switch has little to do with the EPC problem you are experiencing. The brake light normally has an influence on speedo-cruise and has nothing to do with EPC faults which are rather confined to the non-emission related components involved with fuel delivery and torque delivery. The variables are just too many to even guess what it could be. It could be one of many things that could be causing your problem. Even something as minor as a bit of dirt restraining your throttle control butterfly could cause a EPC problem.  Right now you problem could be anything from the crankshaft position sensor to the accelerator pedal position sensor. From your throttle body to the electrical connections, from your high pressure fuel pump to the ECU. I would suggest you have a  scan done then send it to me, perhaps we can try once again to define your EPC problem. I hope you understand my explanation. Cheers Zoe.

______________________________________

Question?

Hola mi amigo, tengo un problema en el polo de mi mujer, y es que se queda al arrancarlo por la mañana del garaje o cuando esta una tarde entera como hoy en la calle que ya hace freskito, como si no subiese de revoluciones,como muy flojo, si le aceleras lo calas, o aveces hace pequeñas detonaciones por el escape, esto le dura unos 20 segundos y ya se espavila. Es un polo 1.4i 80cv, tiene 20milkm, y no ha tenido otro fallo. Posibilidades? 1º Yo creo que puede ser sensor de temperatura de inyeccion, aunque me funcione bien la abuja que mide la temperatura del agua?. 2º bobina? No se que mas podria ser, en dias normales, o si lo arrancas despues de 3 horas o 10 minutos ya va perfecto. Le meti el VAGCOM y no me dio ningun tipo de error. Espero vuestras respuestas

Answer!

Hola a ti. Primero quiero  decir, hablo espanol un poquito pero voy a probar ayudar. Sin error del VAGCOM es mas dificil decir. Apuesto a que es problema de encendido pero dudo es la bobina si le dura de problema porque es solo 20 segundos.  Posiblemente son los bujias o la RON de gasolina no es correcto o tienes agua en la gasolina. Pequeñas detonaciones por el escape no es normal especialmente baja 20milkm. ¿qué pasa con su recien garantía?

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Question?

Hello there, I hope you can shed some light on my problem, I'm having a mini crises with my Seat 1.8L Toledo. The EPC light came on yesterday, but when I turned the engine off and restarted, the EPC light went off and everything was fine until this morning. On my way to work  the car had a jerky/shudder and at that very moment the TC and EPC light came on and I lost power so that it would only rev to  2500 rpm. As a result I limped home them  I plugged in my VAGCOM. Very surprisingly there were no faults. So I decided to take the Toledo back on the road but when I turned on the ignition, the EPC/EM/TC lights came on. So once again I plugged  in my VAGCOM and the DTCs listed below was present. So I cleaned the Throttle Body and  checked the Throttle Body on group 060 and the adaptation field was showing 'ERROR'. What do I do now because I'm totally stuffed and need  a quick fix. Any light you can shed on this problem would be much appreciated.

VAGCOM: Chassis Type: 1M - Seat Leon/Toledo

Scan: 01 02 03 08 15 17 19 22 35 36 37 46 56

VIN: VSSZZZ1MZ3R1XXXXX Mileage: 164400km-102153miles

-------------------------------------------------------------------------------

Address 01: Engine Labels: 06A-906-032-AJQ.lbl

Part No: 06A 906 032 MJ

Component: 1.8L R4/5VT 01 0003 

Coding: 11510

Shop #: WSC 80179 

VSSZZZ1MZ3R1XXXXX SEZ7Z0C2XXXXX

4 Faults Found:

17967 - Throttle Body (J338): Fault in basic settings 

P1559 - 35-10 - - - Intermittent

17987 - Throttle Actuator (J338): Adaptation Not Started 

P1579 - 35-00 - - 

17579 - Angle Sensor 2 for Throttle Actuator (G188) Implausible Signal 

P1171 - 35-10 - - - Intermittent

17951 - Angle Sensor 1 for Throttle Actuator (G187): Signal too Small 

P1543 - 35-00 - - 

-------------------------------------------------------------------------------

Answer!

Hi Wayne, I'm glad to see that you uploaded your scan. Since the rest of your electronic modules have "No fault code found" beneath them, it essentially means that they are all OK. And seeing that you own a VAGCOM, I take it for granted that you may have had prior DTC which you erased. Erasing DTCs are OK but bear in mind that you also erase all values learnt by the ECU associated with your driving style including adaptation values.  The throttle body therefore needs to be re-adapted every time codes are cleared or control module  or battery power is disconnected. As the automatic adaptation software procedure runs, the control module learns the full range of throttle positions. So from what I can see above, the Idle Speed Control Throttle Position cannot be determined which could mean adaption needs to be done, or that the potentiometers in the throttle body may be near end of life. Overtime the slider wears through the carbon track so it makes intermittent contact and stymies the ECU. But before we condemn the throttle body, I need you to disconnect your battery at the earth terminal so that you can hard reset all the electronic modules. Make certain that the ignition is off  then reconnect the battery. Redo a scan and if all goes well, you will once again see your original 4 faults and 1  additional fault that looks something like "Supply Voltage Terminal 30: Signal Outside Specifications - attery/Generator supply faulty". This is absolutely normal because the ECU detected that the battery was disconnected. Plug in VAGCOM switch on the ignition but do not start the engine. Select VAGCOM 04-Basic Settings - which displays the Measuring Value Block screen. Select Measuring Value Block 060 (or 98) which displays the Basic Setting Value Block screen.  Channel 4 will display the word“Running” and other channels will display  the state of the throttle valve angle sensors but will change as the throttle is actuated by the ECM.  Please do not touch the throttle pedal nor turn  ignition key off during the adaptation because the throttle body adaptation relearn process is essential and may prevent the engine from starting if interrupted. If the adaptation was successful, Channel 4 will have changed from “Running” to “OK”. Display 3 would read "idle" and 1 & 2 display voltages levels, normally less than 5 Volts.  Logout, turn the ignition key off and wait about 1 minute seconds, to ensure that adaptation settings are saved then start the car. If however, it still shows "error" inspect the throttle body actuator connector contacts for damage or corrosion and make certain its contacts are secure then try to set adaptation again. If it still shows "error" clean the throttle body and check for wiring harness between the throttle body and the control module. Retry adaptation once again. As a last resort replace the throttle body because the potentiometers cannot be replaced as a separate item nor is it available for sale as a separate item. I hope this helps.

DRIVE BY WIRE

VW - DRIVE BY WIRE (Drive-by-Wire)

If you arrived on the VW Polo website because you searched for  Drive by Wire (DBW), EPC, or EPC light or engine won't rev, Steer-by-Wire, or limp mode,  then you have certainly arrived at the right place. There are several definitions for ECP, the first of which will be explained, is Electronic Parts Catalog (EPC).

EPC stands for Electronic Parts Catalogue (EPC) and all Audi, Volkswagen,  Skoda and SEAT parts are listed in ETKA V7.2 EPC (Electronic Parts Catalogue). This catalogue is purchasable online and downloadable but the file is huge. Companies like Mercedes Benz, Toyota,  Enigma, Attrakt among many, many others host computer based electronic catalogs of the individual auto parts and accessories that make up their engines, cars, tractors, specialized machinery and farming equipment etc. Restated, an EPC is a catalogue in electronic format much like CVS data or a database file or similar, that can be downloaded or is accessible online.

Then there is the second type of EPC - Electronic Parts Catalog (EPC) software. MultiCat and Msys.EPC are companies that specialize in the software that can display an exploded view of an assembled device. For example, the exploded view of an engine, or gearbox, or cylinder head, showing the individual bolts and nuts, flanges, hoses and brackets, etc. and their component part numbers.

Thirdly, there is also the Electronics Parts Catalog (EPC) which is an electronic list or database of semiconductor components, from diodes to transistors to integrated circuits to thyristors, etc... This EPC is often called and equivalents book or catalog and hosts the specifications of semiconductors from several manufacturers. A typical EPC is the RS Electronic Components and Tools Database. This EPC doubles up as the third type of EPC which is the Electronic Product Code. Component Product Codes look like,  1N4148 or BC337, MCP2515, TYN812RG, etc... for electronic components.

However, there are many more EPC definitions, some of them can be found at the end of this blog. I could explain all of them individually but none has any relevance to the subject at hand, viz EPC - Drive by Wire. Drive-by-Wire also know as  DbW, Steer-by-Wire "x-by-wire" or simply "by-wire".

DRIVE BY WIRE

And finally, the Electronic Power Control (EPC) that freaks out almost each and every VW 1.6 Polo, Audi TT, Skoda, SEAT and  Golf TDI, owner. Most vehicles with Drive by Wire [Drive-by-Wire (throttle control)] usually have a Electronic Power Control (EPC) indicator lights on its dashboard which lights up when  there's a problem with the Drive-by-Wire system. This would involve the two accelerator pedal sensors G79 and G185 and in some cases the two sensors G187, G188 inside throttle control valve body - control actuator. [As discussed in my previous blogs] When the engine idles, neither the Throttle Valve Angle Sensor nor the Accelerator Pedal Position Sensor are monitored for faults by the ECU, as such, the engine does not respond to accelerator input but will limit engine to 1200 RPM.

The  basic components that constitute the Electronic Power Control (EPC) circuit. 

There is no throttle cable involved, because its an electronic throttle control.

The Electronic Power Control (EPC) circuitry consists of EPC light, Accelerator Pedal, Throttle Control Valve,  DBW  (no throttle cable,) Injectors and the Engine Control Unit (ECU). Have a look at the diagram above. The inputs to the ECU is marked green and the outputs from the ECU is marked blue.  Check that the brake light bulbs are OK, if not check the brake fuses. There are other inputs to the ECU from numerous other sensors or units for example the Automatic Gearbox Control unit, Cruise control unit, Air conditioning unit, Lambda Regulation unit, Knock Sensor units, Alternator, Engine Speed Sensor unit, ABS and the  Power-assisted steering unit to mention but  a few. 

The CAN-Bus bidirectional connection is marked in orange. Some of the other inputs like Knock sensors and Lambda regulator and Engine Speed Sensor unit can also cause the EPC light to come on. If the Engine Speed Sensor unit is responsible, it will reset itself after a while and if the Lambda regulation is faulty the vehicle will smoke and turn on both MIL and EPC lights, but if the Drive-by-Wire - DBW (not drive by cable) system is faulty then only the EPC light will be on.

Both the accelerator sensors and the throttle valve sensors work on the same principle since all 4 of them are potentiometers. The input voltage is 5 Volts and the increments are in millivolts implying that there is an  acceleration range of between 0 and 5000.  Throttle valve angle  sensor 1 and Throttle valve angle sensor 2, Accelerator position sensor 1 and Accelerator position sensor 2 sliders makes contact with the resistive track and outputs the appropriate voltage level to the ECU. These resistive tracks are prone to go faulty since they are gold plated contacts running on gold plated copper tracks etched on a PCB. Over time the contacts wears right through the gold and copper plating, only making contact with the bakelite or fibreglass substrate. This type of potentiometers are less reliable than ceramic thick-film potentiometers.

When the EPC warning light goes on and your acceleration goes limp and the engine won't rev-up there is an easy cure but there may be exceptions. Get the car home even if it means driving really slowly in "Limp Mode". Once home, disconnect the battery for about 15 minutes or so, but not more than 20 minutes then reconnect. NB! do not disconnect the Live terminal, disconnect the Earth terminal. If the battery is disconnected for more than 20 mins you will lose your radio settings since the radio also participates in volatile and non-volatile memory of  the CAN-Bus. 

Reconnect the battery but make certain that the ignition is off. Once this is done, turn on the ignition so that the dashboard lights go on but do not start your car and DO NOT touch your accelerator pedal. After about 5 minutes the throttle body will aligns itself. After 10 minutes turn off the ignition, wait for 2 mins then start the car and let it idle for abut 2 minutes as well. By now, the EPC warning light should be off and the engine will rev as normal.You may have to to this twice. If this worked for you, please do give me some feedback with a comment.

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