Volkswagen and Audi EPC

Volkswagen and Audi EPC

The Internet is a huge repository of  information, some useful  and some not so useful, or more to the point, useless. But, there is so much of both, duplicated and reechoed  in posts like auto-facts, axleaddict, youfixcars, and motor forums by so many individuals. There is nothing worst than being led up the garden path by some ignoramus who knows squat about electro-mechanical engineering technology when you are desperately looking for answers. To reduce that from happening, I decides to bust some of the myths related to VAG cars that are being echoed over and over and over.

EPC can be a bitch to repair.

Myth 1
Here's the first myth from someone on Yahoo Answers, relating to a 2012 VW Polo. "You can clear fault codes by disconnecting your battery for a while".  And here's another, "just disconnect the battery on your Audi A3 for a little more than 10 seconds and your fault codes will be  gone"! 

Myth 1 Busted
Though the above is true for pre-1996 vehicles fitted with OBD-I, disconnecting the battery on any car manufactured post-1996 fitted with OBD-II will definitely not delete any fault codes because the ECU stores all DTC (Dignostic Trouble Codes) aka fault codes codes in its  non-volatile memory.  What it will do, is reset the cpu / timer. The term non-volatile memory is generally used for all types of solid state memory, meaning memory that doesn't need its contents refreshed periodically. 

However, the ECU also stores learnt values and basic settings, like for example the Fuel Control Learning Adaptation Values and the Kick-Down Position of the Accelerator which is needed by the automatic transmission. This data and your car's radio code is not stored in non-volatile memory and will undoubtedly be erased when the battery is disconnected.  Once the battery is reconnected, the adaptation process needs to be done which will enable the ECM to learn the new settings for the Drive-by-Wire electronic throttle  valve and store it. If you didn't save the radio code you have to go to a VW / Audi dealer with your VIN and they may be able to give it to you.

When you disconnect your car's battery, the ECU detects the loss of battery power and registers a DTC in the ECU's non-volatile memory to that effect. This record can be seen after the battery is reconnected and a  diagnostic scan is performed.  It would look something like this,

2 Faults Found:
00532 - Supply Voltage B+ 
            07-10 - Signal too Low - Intermittent

01598 - Drive Battery Voltage 
            07-10 - Signal too Low - Intermittent

Removing the negative terminal of the battery isn't all bad, it does have the advantage  of resetting  the system's ECU safety watchdog timer. A safety watchdog timer (WDT) is responsible for periodically generating a system reset in the event of a software glitch. This one of a kind CIC61508 safety watchdog timer is ASIL-D (Automotive Safety Integrity Level D) approved,  where level D refers to the highest classification of initial hazard against the risk of injury as defined within ISO26262 automotive industry standard.

Infineon Safety Watchdog timer 

Pressure Sensors

Myth 2
There are pressure sensor in the VW and Audi engine block that causes an EPC light to come on and make the car go into limp mode.

Myth 2 bustedYes, there are pressure sensors in both VW and Audi engines but they not fitted into the block and should not be mistaken for than for knock senors that are screwed to the block. Faulty or loose knock sensors can cause the EPC light to come on and send the car into limp mode.  The baro sensor measures the ambient air pressure and has a effect on engine performance altitude dependent.  The supercharger boost pressure is controlled via the regulating flap control unit Intake manifold pressure sensor/MAP sensor (MAP = Manifold Air Pressure) which can cause the EPC light to come on and send the car into limp mode. The high-pressure fuel pump delivers fuel at a pressure of up to 150 bar and any drop in this pressure can cause the EPC light to come on and send the car into limp mode. Common problem with loss of pressure is the fuel filter. Loss of oil pressure can cause the EPC light to come on and send the car into limp mode. Lastly there is high system pressure in the cooling system at high revs and sudden loss of this pressure can cause the EPC light to come on and send the car into limp mode.

Myth 3
EPC light usually means that the Electronic Throttle Body needs replacing and reprogramming.  

Myth 3 busted It is advantages to perform adaptation on the throttle body, before attempting to replace it with a new throttle body . Often times replacing it makes no difference and normally turn out to be the wiring harness connectors to the throttle body that's defective.   Disassemble the three electrical connectors around the throttle body clean  this inside of the connectors with circuit cleaner and reassembled. Also check for vacuum leaks, especially pressure regulator hose and the small pipes connected to the intake-manifold before replacing anything.

Myth 4
Epc light is mostly known to come on when there is emissions problems. 

Myth 4 busted This is incorrect because the 'check engine light' is specific to emission related problems, however The EPC light may also come on if the emission related problem affects the engine torque. So repairing the emission related problem first would in most cases reset both the EPC light and the 'check engine light'.

Sensors associated with EPC

Extensive safety measures have been designed and implimented 
in both the hardware and software of Audi and VW.  In most cases dual sensors are used for continual self-checking of signal plausibility. A safety watcg dog timer is integrated in the Motronic ECM to constantly and continually monitor the processor for correct and proper operation. Some of the sensors are listed below.

Fuel Pressure Sensor G247
Low Fuel Pressure Sensor G410
Oil Level Thermal Sensor G266
Heated Oxygen Sensor (HO2S) G39
Heated Oxygen Sensor (HO2S) 2 G108
Oxygen Sensor (O2S) G130 &  G130
situated behind 3 Way Catalytic Converter (TWC) G130
G186 Throttle Drive  (EPC))
G187 Throttle Drive Angle Sensor 1  (EPC))
G188 Throttle Drive Angle Sensor 2  (EPC))
Engine Speed (RPM) Sensor G28
Mass Air Flow (MAF) Sensor G70
Throttle Position (TP) Sensor G79
Accelerator Pedal Position Sensor 2 G185
Clutch Position Sensor G476
Throttle Valve Control Module J338 
Throttle Drive Angle Sensor 1 (EPC) G187
Throttle Drive Angle Sensor 2 (EPC) G188
Camshaft Position (CMP) Sensor G40
Camshaft Position (CMP) Sensor 2 G163
Engine Coolant Temperature (ECT) Sensor G62
Engine Coolant Temperature (ECT) Sensor G83 (on radiator) 
Knock Sensor (KS) 1 G61
Knock Sensor (KS) 2 G66
Brake Light Switch F

My EPC light

My EPC light

If you've had your VW, Audi, SKODA or SEAT for a while, you're probably familiar with the EPC light and already experienced its wrath. If you haven't encountered the EPC warning light as yet, then you are definitely one of the lucky ones, because I know of several VW Polo, Seat Ibiza,  VW Jetta, VW CC, Passat, Audi A3, Audi A6, Seat Leon and even Porsche owners with odometer readings as low as 1500 Kilometers, who got spooked by the EPC light when it first stuck. This EPC light is known to trigger instant panic and fear in many VAG car owner, and I don't blame them, since it can be a scary and dangerous experience, especially when the car goes into limp mode when you're overtaking or the engine just dies when exiting a freeway  off-ramp or when entering a highway on-ramp during peak hour traffic.  

Electronic Power Control

However, if you have no idea what an EPC light or an EPC fault is, nor why this warning light turns on, then you should do yourself a solid and continue reading. In a nutshell, the EPC warning light is a standard feature in all ODB-II compliant models of Volkswagen, SEAT, SKODA and Audi vehicles. Most of them, are fitted with 'drive-by-wire' technology, though neither are exclusive to VAG cars. And when I say VAG cars, I also mean  Porsche, Bentley, Bugatti, Lamborghini and Ducati. Toyota, Honda, Ford, Mercedes also has it, in fact, virtually all cars manufactured post 1996  have an EPC warning light. EPC is an acronym for Electronic Power Control, and its a  warning light that resides inside the instrument cluster display.

EPC Light

Nonetheless, the EPC light is not all doom and gloom. It is there for a reason, and that reason is to safeguard the car and the engine from damage or destruction, especially considering what they cost to repair these days, let alone the cost to have an engine overhauled. Many people are under the misapprehension that the EPC light indicates an issue  with the cars  computerized system, whereas mechanics tend to echo that the EPC light indicates  a potential engine malfunction, though that's not strictly true either.  

MIL 

Before we continue, I just needed to add that when the engine malfunctions, it illuminates the Malfunction Indicator Lamp (MIL) aka Check engine light (CEL), which is indicative of  a computerized engine-management system malfunction. It even has an amber/orange icon of an engine, so as to draw your attention to the engine. Furthermore if this amber icon engine light is steadily illuminated, it indicates a minor engine fault but when it blinks it signifies a major engine fault. On the other hand, the EPC (Electronic Power Control) warning light  is a distinctly separate light from the MIL or CEL because it is related to a different function.

The more appropriate answer to 'What is an EPC light?' would be that the Electronic Power Control warning light, indicates a malfunction in your VW, Audi, SKODA or SEAT's  throttle control system, though once again that's also not totally accurate either.  So let me throw so light on the subject. The EPC light is in fact a diagnostic test light. So when the car's ignition is first switched on, the EPC light is illuminated for about three seconds. If there are no faults in the EPC system the light will automatically extinguish.

Drive by Wire

This three second time period is the duration of a self-diagnostic test. Effectively the Motronic ECM (J220) checks for malfunctions  in the Electronic Power Control (Torque system) accelerator system (drive-by-wire system), which includes the Throttle Body Drive Stepless Motor (G186) with its dual   independent Throttle Drive Angle Potentiometers (G187 & G188), the Accelerator Pedal Module with its dual independent Throttle Position Sensing Potentiometers (G79 &G185), the wiring harnesses that connects them all together and its associated sensor inputs from the Cruise Control  System, the Anti-lock Brake System (ABS), the Oxygen Sensor Control, the Automatic Transmission and the Air Conditioning System, etc. 

Charge Air Path

Here Air conditioning system mean all components involved in conditioning the air in the inlet manifold prior to combustion, implying the Throttle body / Mass Air Flow (MAF) sensor G70 and not A/C as in HVAC.  That being said, the functionality of an Electronic Throttle Control (drive-by-wire system) can regulate the Charge Air Path far more accurately than a physical cable between the accelerator pedal and the throttle valve. 

NonVolatile Memory

This being the case, by the time the EPC light illuminates on the dashboard  in response to some sensor detecting a problem  whilst driving, the problem already occurred.  The  EPC warning is just a way to tell you that there  was a glitch in the EPC (drive by wire system) and generally remains lit until the fault is cleared. The EPC light is known as K132 and is turned on by the Motronic ECM by providing the Ground  connection that keeps the light burning. At the same time, a DTC is registered and stored in non-volatile memory for later inspection.

Limp Mode

So the key piece of equipment to solving any EPC problem or issue is a diagnostic scanner. The fault below shows that the brake light switch F was the culprit that caused the EPC fault. Bearing in mind, that the Cruise control get its cancellation signal from the brake light when the brake pedal is depressed. When a brake light is fused or the dual contact brake switch goes open circuit and can't provide the requisite signal, the cruise control cannot be cancelled. The ECM detects this condition and construes it as a safety issue and sends the car into limp mode. 

Fault Codes

Essentially the EPC circuit prevented an accident from happening. Implying the brakes would work but the engine would still run at high rev set by the cruise control, meaning the brakes would be ineffective to bring the car to a stop. For safety reasons the EPC system closes the throttle valve to a predetermined position the brake pedal and the accelerator pedal are depressed simultaneously. However if the ECU detects that the brake was depressed before the accelerator, then acceleration will be carried out. 

1 Fault Found:
16955 - Brake Switch (F) 
P0571 - 35-10 - Implausible Signal - Intermittent

The fault below shows  that there is  an electrical malfunction in the Drive by Wire  circuit causing the EPC light to illuminate. After clearing the fault code, the EPC light just comes back on. The ECU was suspected and replaced but didn't solved the problem. It turned out that the  wiring harness between the ECU and the instrument cluster.

1 Fault Found:
18084 - EPC Warning Lamp (K132) Circuit: Electrical Malfunction 
P1676 - 35-00 - - 

The fault below  was on an Audi where signal from the Transmission  Control Module (TCM)  to the ECU was intermittent causing her to go into limp mode and idle really rough. Turned out that the TCM got wet from rain water that leaked into the carpets.  

1 Fault Found:
18265 - Load Signal: Error Message from ECU 
P1857 - 35-10 - - - Intermittent

EPC DASHBOARD WARNING LIGHT

EPC DASHBOARD WARNING LIGHT

VW, Audi, Skoda and SEAT vehicles are crammed with wonderous technology, ranging from various electronic modules that overseas their general functionality to hoards of sensors that monitor how these vehicles behave and actuators that respond to software controlled decision making elements. One could say that collectively they give cars a degree of Artificial Intelligence and their seamless integration makes motoring a lot easier. But when something goes wrong, there is also a swarm of warning lights on the instrument cluster that will flash at you until you take corrective action. However, knowing exactly what each warning light flashing on its dashboard is trying to tell you, is a completely different story. Even though some of these light are self explanatory and fairly obvious to understand, others are not, and  can be interpreted by looking in the owner’s manual. Knowing what these warning lights mean is really important to drivers because they can preempt a potential breakdown or full-on engine failure, insulating you from expensive repair bills.

As a general rule, warning lights illuminated either red or amber (yellow /orange), though a blue light is often used to indicate high beam and green lights are used to mean indicate left and right  turn signals. On a VW Polo a red warning light emphatically means that something needs to be done immediately. For example, the Oil pressure warning light, or the low brake fluid level light, or the parking brake warning light, or the Coolant level low / coolant temperature high light, illuminates red or flashes red as a danger sign and needs immediate attention. Failure to remedy can result in the engine seizing, the brakes failing, damaging your rear disks and brake pads, or the engine overheating resulting in a possible blown head gasket or worse, respectively. On different model VAG vehicles, the use of red and amber light may overlap. 

An amber / yellow /orange light  on the other hand serves to be rather informative and draws the driver]s attention to a potential problem or a problems that needs to be remedied soonest. For example the amber Anti-lock braking system (ABS) light, or the amber Airbag light, or the amber Immobilizer light, or the Brake pad wear light, or the Engine fault Onboard diagnosis (OBD) light, none of which will impede driveability nor endanger the driver. But this isn't strictly true especially when encountering the dreaded yellow EPC light. 

WHAT IS AN EPC LIGHT?

EPC stands for Electronic Power Control and has  much to do with controlling the electronic throttle hence it is sometimes referred to as the "Electronic Pedal Control". Probably because the throttle valve is actuated by an electric motor rather than a physical cable between the accelerator pedal and the throttle control valve. In essence the engine control unit responds to the sensor on the accelerator pedal and sends a corresponding command to the throttle valve positioner via four wires which is commonly known as "Drive by wire". But the EPC is much more than just an Electronic Pedal Control. Any malfunctions in the either the "Drive by Wire" circuit  or its associated sensors are detected by self-diagnosis and indicated by the EPC warning light.

The Electronic Power Control (EPC) is a circuit made up of various engine components or sub circuits that collectively addresses torque. In reality it should have been called "Electronic Torque Control". Should  a problem arise in the torque system, it correspondingly illuminates the easily identifiable yellow/amber/orange word "EPC" in the instrument panel.  The EPC circuit's decision making elements are embedded into the ECU which is responsible for the electric throttle valve positioning and overall torque-oriented engine management.

As such the ECU has to gathers all torque demand inputs in order to correctly calculate the appropriate control actions. These inputs includes, the Engine speed, the Engine load signal fetched from the air mass meter, the Vehicle speed, the shift point of an automatic gearbox, whether or not the air conditioner compressor is ON or OFF, whether or not the the cruise control system is engaged, whether or not the Traction Control System is engaged  or the braking  system is applied.

The combination Brake light / brake pedal switch provides a braking input to the ECU, failure of the switch to send data of the drivers foot on the brake pedal can trigger the EPC light in certain VAG vehicles, but definitely on the VW Polo. Don't be fooled by the brake lights that are working, when the brake pedal is depressed because it does not imply that the brake pedal switch is functioning as it should. In similar fashion the Clutch Pedal Switch provides cruise control input to the ECU, engaging the clutch, automatically disengages the cruise control which could also trigger an EPC episode.

This EPC light will come on when there is a problem:-

1) With either of the accelerator pedal senders.
2) With either of the throttle angle senders.
3) With the throttle valve control unit
4) With the accelerator / throttle harness.
5) With the throttle adaptation.
6) With grime and carbon build-up in the throttle body. 
7) If the the Throttle Valve Control Unit is replaced.
8) With the Brake Light Switch
9) With one of the Knock Sensors.
10 With the Mass Air Meter (MAF).
11) with the Engine control unit
12) With the Ignition system
13) With the Fuel injection system
14) With the ABS
15) With the Power-assisted steering system
16) With Lambda regulation (fuel consumption signal)
17) With the Alternator
18) With the TCM

Bearing in mind the throttle valve control unit is located on the intake manifold and needs to ensure that the engine is supplied with the appropriate and proper air flow. By implication the MAF measures the air flow and should there be a problem with it, the  ECU will not be able to calculate the proper torque and possible go into EPC mode. The consolation is that every fault that occurs would normally create a DTC entry. So the best way to determine the cause of the EPC light coming on, associated with loss of power and limp mode, is to do a diagnostic scan. 


Links to other EPC Problems!
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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.

LIMP MODE Q&A

LIMP HOME MODE

When I initially bought my VW Polo 2.0L she was a thrill to drive. Her speed was instant, cornering was really good and road holding never better. She was a joy to drive, very unlike my VW Golf II, but then I started getting car troubles,  which were many and varied. My first encounter with VW agents was a disaster. After they "repaired" my EPC fault they charged me a ridiculous sum of money, only to experience the same EPC problem the following day.  After speaking to several of their mechanics, who collectively were unable to fix my car, I came to realize  that I was either far more knowledgeable about automotive electronics than all of them put together, or they knew very little about electronics.  This just put me off the agents completely and when I took my Polo to independent mechanical workshops,  I found the same to be true. I still remember how lost I felt when my VW Polo went into limp mode the first time and the second and the third and the fourth. I felt lost, stuck on the freeway, late for meetings, frustrated and miserable because I couldn't repair her like I did the VW Golf II due to the fact that the Polo had OBD-II. I  thought my VW Polo to be unreliable, there was a point that I feared driver her at night, and later started to hate  even diving the Polo.  I was literally on the verge of setting her alight. But them I decided to buy a Ross Tech cable and downloaded their VCDS and my Polo is a joy to  drive once again. The rest of this blog is devoted to 10 vehicles owners who have experiences similar trouble with their VAG vehicles ranging from Drive by wire problems, to EPC trouble, to DTC trouble Codes to CAN-Bus-issues to name but a few. 

DRIVE BY WIRE
Steve sent this:- Had the problem of no power, tried the technique described in your blog (disconnect battery, wait, reconnect, turn ignition key, wait, turn off, turn engine on, wait, press throttle...) - and it worked beautifully. Many thanks for your help, very much appreciated - particularly as you've probably save me many pounds. 

QUESTION? - DRIVE BY WIRE
Anonymous sent this:- I have a '07 Polo 1.4 16v BUD. I don't have any lights on the dash, but the engine seems really weak through mid revs and is using a bit too much fuel. When I hook up my OBDII there are no faults recorded but when I view the throttle position in real time it doesn't seem to open in a linear manner. As I press the pedal on the road, the throttle valve seems to open slower than the position of  the pedal. eg; 50% pedal = 30% throttle position, 80% pedal = 35% throttle, 95% pedal = 40% throttle, 100% Pedal = 100% throttle. As you can see WOT does give WOT at the throttle body, but I don't generally drive with my foot planted on the floor. I am confused why it does this as you would expect the throttle body to open the same amount as the pedal, could it need alignment? I am loathed to take it to the VW dealer for fault diagno$i$ so if anyone has any ideas????  Thanks 

ANSWER!
On drive by wire model vehicles the throttle doesn't open like legacy cable throttles because its electronically controlled. 

DRIVE BY WIRE
Durell  Dunn  left this:- I am currently experiencing the same problem with my 2003 polo,1.4. The car goes into limp mode and on some occasions switches off in traffic, hectic ! I will use your method. Thank you for saving me from going to a VW dealership, all I can do at this stage is do and hope 

DRIVE BY WIRE
Loci sent this:- Hi. I have a problem with my Volkswagen Polo 1.4 Tdi. It seems to have a good start but after I drive for around 35 minutes it loses the power so I could not pass 2000 giro. Thank you for your suggestions.

QUESTION? - DRIVE BY WIRE 
Anonymous asked:- My car is a polo 1.4 2012 model. When I start the car the EPC light switch on then I put gear to move the car but it limbs then I switch it off then start it again then the EPC light does not switch on then off I go... What could be wrong? 

ANSWER!
The trouble can be one of many things, among which are your accelerator pedal, throttle body, knock sensor, Fuel pump pressure, even a loose fuel cap. You need to check through each systematically but for that you at least need a scan of your vehicle.

ENGINE LIGHT COMES ON
Lee Kyprian left this:- Everyone who has ever owned a car has experienced the confusion and even panic which can arrive when your check engine light suddenly comes on.

QUESTION? VW ELECTRONIC POWER CONTROL
Abror Isoqov sent this:- Hello. My car is VW Golf 1.6 16v and I have a problem with acceleration it has no enough power. It accelerates very slow and at 5th gear it can get max 130 km/h. At neutral position when engine gets about 5000 rpm the EPC light comes on. After restarting the engine it goes off. Tester didn't determine any trouble codes. What can cause for this problem. I went about 7-8 auto services but any of them could help. But I didn't go to VW dealer because it will be very expensive. last time they charged me $125 just for diagnostic.  Please help me with this issue.   

ANSWER!
What you explaining is limp mode and everything else seems very odd. Because by the time the EPC light does go on, a DTC is already set which any scan tool should be able to retrieve. Unless there is a problem with you DLC wiring, so that communication between vehicle and scan tool is erroneous.

VW ERROR CODES
Steve Cain sent this:- Hi, vw polo 1.4tdi 2003, AMF engine code,  problem is that when driving at any speed, car looses all power, engine stuck on 1200 rpm, throttle pedal no response, glow plug heating light flashes, switch off & switch back on straight away, car drives normally, no warning lights. Can you shed any light on this problem, (driving my wife mad). Thanks, Steve 

ANSWER!
I have covered this problem quite substantially in previous blogs and it in your interest to ready through them.

WON'T REV
Anonymous sent this:- My VW Jetta 2002 1.8t stopped me on the highway and it refused to rev and the mechanic says it is the brain box. I don't understand is he correct?

ANSWER!
Yes he is correct, problem lies in the ECM circuit but not necessarily the ECM itself. Dude you need to get your car scanned to get a better idea of  the actual problem.

CAN-BUS
Hi! I read your blogs and saw writings from you  about the CAN bus protocol. I have a problem to understand something on my cars OBD connector and the CAN bus line. Can you please help me maybe? Can we talk about? When I connect my 2 channel  DSO to the OBD connector pin 6 and pin 14 ( CAN-H and L ) and pin 5 (GND) on my VW Polo 1.4D year 2003 I got this signal what I posted right now. But, when I do the same think on my Renault Clio 1.5DCI year 2003 I got the right CAN signal.  

ANSWER! 
The likely hood is that your VW Polo isn't CAN compliant because its still a 2003 and used KWP-1281 and KWP-2000 protocols.  All VW's after 2008 is fully CAN compliant.

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.

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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?

______________________________________

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.

TORQUE RELATED EPC ISSUES

FUEL PRESSURE EPC PROBLEMS

EPC problems are a pain in the butt, they just complicate your life, make you late for appointments, leave you stranded on highways when you least expect it.  Makes you curse and cuss and make you want to fit a accelerator cable but these issues as not limited to VAG cars, as can be seen in the pics. At times EPC faults even endanger your life when they occur on the freeways, especially in fast flowing traffic when limp mode doesn't even enable you to get your vehicle off the road and out of harms way quick enough as not to be the cause of an accident. EPC fault are so darn frustrating. EPC faults are so  time consuming and EPC faults are so expensive to repair, hence many a VW, Audi, Skoda and Seat driver attempts to self diagnosis and repair their own vehicles. I have found that EPC faults can be really crappy to diagnose because the ECU's  firmware and switching hardware is in control and operates at high speed and therefor cannot be measured, unless you have a multi-channel digital storage oscilloscope. Since there are not ECU timing charts available to accurately pinpoint the causes of ECU problems, we hear many stories, in which the VW, Audi, Skoda and Seat agents are stymied by the EPC light, loss of acceleration and limp mode home. Several Audi, VW, Seat and Skoda driver can relate such stories. Stories  of taking their vehicles to the relevant sevice agent only to be told that they found nothing wrong, with the car, they then clear the DTCs saying it was just a sporadic / isolated event or often times they suspect and change some expensive components,  exorbitantly  bill for it, yet never solve the problem because within two or three days the EPC problem strikes again. This peculiarity of the EPC problem tends to go away the following day and the car drives as if there was never any problem. It is so intermittent that the vehicle just borders on becoming unreliable. That really sucks.

What I have found,  is that when an EPC related problem occurs, a DTC is flagged and stored in memory for later retrieval, meanwhile the EPC light is triggered and stays on, with the result that the engine only revs to 1200 RPM. Since the light is already on, even if a second or third EPC problem occurs, there is no way to tell because additional EPC problems won't make the yellow /amber EPC light glow any brighter. However if the DTC of the first EPC fault is different from the second of third, additional DTCs will be observed when the memory is retrieved. Should an EPC fault occur and trigger the EPC light, and a second is not undetected over a successive distance of approximately 1000 km, it is automatically erased from the memory and the EPC light will go off. EPC light problems are predominantly found on electronic Drive by Wire systems because they are torque driven. Whenever a problem occurs in the electronic Drive by Wire circuit, the EPC circuit / system acts as a safety measure to prevent injury to the occupants and the car itself by going into limp mode.

It is quite common for the PWM Signal from the ECU to the fuel pump control module to fail, resulting in the EPC light switching on and the vehicle going into limp mode. It is quite easy to verify whether or not the ECU was at fault because by disconnecting the battery and reconnecting it  after a few minutes, it resets the ECU's clock since it doesn't have backup power.  Removing the battery does not delete DTC memory nor the learnt ECU adaptation values so its quit safe to do. It however triggers a  manufacturer specific 18010 DTC - Power Supply Terminal 30 missing, or a generic P1602 DTC -Voltage too Low, Intermittent  which will be sen the next tie you connect to a scan tool.

Normally whenever the ECU detects a fault, like a missing pulse or an intermittent connection it calculates a substitute value from other available signals and makes an emergency running mode available to keep the vehicle driving.  I have noticed what's different between the electronic Drive by Wire systems and the rest of the on-board systems is that the ECU does not provide a substitute signal for torque related  / electronic drive by wire faults. So if either  G79 or G185 or both fails,  it results in no throttle response but the ECU does not generate a substitute signal, it rather just goes into emergency mode and switches on the EPC light. Like wise if G187 or G188 or both fails also, resulting in no throttle response the ECU again does not generate a substitute signal but rather goes into emergency mode and switches on the EPC light. When N30, N31, N32 or N33 fails or any of the the Ignition Coils fails, the  EPC light as well as the Mil light switches on but since the engine runs rough, its easy to isolate and remedy. When the wastegate bypass regulator valve or the fuel pressure regulator valve  fails, frustrating limp mode and the EPC light once again spoils your day.

KNOCK SENSOR

VAG KNOCK SENSOR K1 AND THE EPC LIGHT

VW, Seat, Skoda  and Audi Knock sensors have become quite notorious for sending the car into "limp mode". Limp mode is a safety feature on all Drive by Wire vehicles, implying an EPC-electronic power control-but no accelerator cable. EPC implies torque control. By analogy,  its something like a horse that gets spooked and takes off at high speed and out of control with its rider unable to rein him in,  or a frayed accelerator cable that becomes stuck while driving at high speed. That's just a recipe for disaster. Imagine stepping on the brake pedal but the high revs of the engine just forces the car forward, smoke pouring from the brake pads to the point that the become glazed and  no longer has any effect. Pushing the transmission into neutral isn't an option because without the load, the engine is destined to blow, perhaps even push a piston  through the side of the engine lock.  Drive by wire prevents this from happening and cuts power to the powertrain if it detects a fault that puts the engine at risk. Knock reacts somewhat similar to backfire since both are due to detonation and pre-ignition-incomplete combustion.

Detonation is a common problem associated with lean fuel mixture -non stichometric-and torque. The EPC light is often triggered on an incline when the torque is insufficient to pull the car uphill when in an inappropriate gear. Knock sensors can detect combustion knocks in individual cylinders. Knock sensor 1 (G61) senses cylinders 1 & 2, and knock sensor 2 (G66) senses cylinders  3 & 4. To prevent combustion knock, the ECU cylinder selective knock control overrides the electronic control of the ignition timing by retarding the timing, but may not be unable to if the Fuel Octane is too low causing secondary combustion in the cylinder. Knock sensor 1 (G61) is known to trigger EPC light and activate limp mode, hence it needs to be checked for flush engine contact and correct torque. DTC  P0171 and P0174 could show up in scans.

The ECU calculates engine ignition timing based on input signals from Throttle Position (TP) Sensor G79 and  Accelerator Pedal Position G185, the  Engine Speed (RPM) Sensor G28,  the load signal from Mass Air Flow (MAF) Sensor G70, the signal from the Throttle Valve Control Module J338,  the Coolant Temperature (ECT) Sensor G62, both Knock Sensors G61, G66 (additional G198 & G199 on V6, W8 & W12 engines) and signals from Camshaft Position Sensors G40, G163, (additionally G300, G301 on V6, W8 & W12 engines) When the engine is below 40 degrees  celsius knock sensors signals are not used to make timing decisions. What this implies is that when the EPC light turns on  when the engine is still cold, the knock sensors are not guilty , neither  the the Mass Air Flow (MAF) Sensor G70 nor the Coolant Temperature (ECT) Sensor G62 since whilst idling, have nothing to do with torque. That leaves the Accelerator Pedal with G79 & G185, the Throttle  Control body senders G187 & G188,  the  Engine Speed Sensor G28,  Camshaft Position Sensors G40 & G163 as the EPC limp mode culprits. However sensors are fairly reliable but the wiring  harnesses  are  more likely to be the cause of the problem, see wiring in Audi.

Fuel pressure regulator valve N276, the wastegate bypass regulator valve N75 and the  Ignition Coil N, N128, N158, N163 and its Power Output Stage N122 are three  more EPC culprits. Injectors N30-N33 can also cause the EPC light to turn on and cause car to go into "limp mode" but also causes the engine not to run smoothly. Once again before condemning the sensors or actuators, check the wiring harnesses to them.



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The above EPC errors are common to Volkswagen, Audi, Skoda and Seat. The  VW, the 4motion, the Amarok, the new Beetle, the Bora, the Caddy, the Corrado, the CC, the Eos, the Fox, the Golf, the Jetta, the Kombi, the Lavida, the Lupo, the Passat, the Polo, the Phaeton, the Routan, the Santana the Scirocco, the Sharan, the Tiguan, the Touran, the Touareg, the Transporter, the Vento , the Up and lastly the Vivo. The Audi A1, A2, A3, A4, A5, A6, A7, A8, the Q3, Q5, Q7, the RS4, RS6, RS8, the R8, the S4, S6, S8, Audi TT. The  Seat Alhambra, the Altea, the Arosa, the Cordoba, the Ibiza, the Inca, the Leon, the Mii and the Toledo,  Skoda  Felicia, the Octavia, the Fabia, the Superb, the Roomster, the Yeti, the Rapid and the Citigo. The Audi RS-6, A4 Fsi, Audi A4, Audi S3, Audi TT, Audi R8, audi a4 2.8 quattro 5 speed, Skoda fabia, seat leon, seat ibiza, Avant RS 2, Coupé, Audi A3 Mk1, Volkswagen Golf Mk4, Volkswagen New Beetle, Volkswagen Bora/Jetta Mk4, SEAT León Mk1, SEAT Toledo Mk2, Škoda Octavia Mk1,  TFSI, FSI, GTI, TDI,