AUDI EPC LIGHT PROBLEMS

AUDI EPC LIGHT

It is common knowledge that EPC light problems have been haunting Audi drivers incessantly for the past few years, announcing itself on Audi A1,  Audi A2, Audi A3,  Audi A4,  Audi A5, Audi A6,  Audi A7,  Audi A8,  Audi Q3,  Audi Q5, Audi Q7, the Audi RS4,  Audi RS6, Audi RS8, Audi R8, Audi S4, Audi S6, Audi S8 and Audi  TTs even before they're run-in. Several Audi owners are dismayed that EPC problems present themselves on virtually new cars. 

In fact, EPC problems pop-up at any time, on any Audi new or old fitted with X-by-Wire technology. Any Audi  without a throttle cable, is naturally fitted with a full Drive-by-Wire system which is supervised by the Electronic Control Circuit (EPC)  / Electronic Throttle Control (ETC)  that turns on the dashboard mounted EPC (K132) indicator light when it detects a malfunction, then registers Diagnostic Trouble Codes (DTC)  in the ECM memory.  Even though the EPC light turns on exclusively for  non-emission related faults, it does however turn on along with the MIL for emission related faults. 

The EPC  / ETC is a torque monitoring circuit and monitors for torque discrepancies and torque inefficiencies and when it detects one, sends the vehicle into emergency running mode (limp mode). These are prevalent when towing, when driving up an incline, when in manual mode, when in cruise control, after spirited driving, etc, and may even cause the ABS, ESP   lights to came on. Some drivers, assume  that it's happening more frequently over time and others are concerned that the EPC trouble are going to get worse because of its  randomness. But this is not the case. 

Bear in mind that once the EPC light is on, no other EPC related fault is going to make it glow any brighter. Once it's on, it's stays on even if the battery is disconnected, and it will come back on when you reconnect. However, the ECU will monitor the EPC circuit and if the same error does not occur in three successive trips of at least 7 kilometers, it will erase the DTC and it would seem as if it never happened, until the next time.  These are safely features specific to Drive by Wire systems and their workings can be viewed in the adaptation groups when retrieving errors with a scan tool.

ADAPTATION GROUPS PERTAINING TO EPC

Group 60 -- Throttle Valve Adjuster / Adaptation Epc-system

Group 61 -- Epc-system / Throttle Valve Adjuster (System 1) 

Group 62 -- Epc-system / Throttle Valve Adjuster (System 2)

Group 63 -- Kickdown Function

Group 66 -- Cruise Control Status

AUDI EPC LIGHT RELATED DTC

18039 / P1631 - Accelerator Position Sensor (G79): Signal too High 

18041 / P1633 - Accelerator Position Sensor 2 (G185) Signal too Low

18042 / P1634 - Accelerator Position Sensor 2 (G185): Signal too High

18047 / P1639 - Accelerator Position Sensor 1/2 (G79/G185): Implausible Signal 

 00777 - Accelerator Position Sensor (G79): Implausible Signal

No response from the throttle even with your foot flat on the accelerator pedal.. There are two potentiometers fitted to the accelerator pedal which are monitored by the ECU and when it it detects an intermittent signal from one pot, it turns on the EPC light then uses the second pot for acceleration but it is limited. When both pots detected as are intermittent, EPC light goes on and engine only runs at idle speed. When this error occurs, turn the engine off, stomp on the accelerator a few times through its full travel.  It could just be specks of dust that settled on the one of the potentiometer (variable resistors) tracks that stymied the ECU for a few millisecond or so. I this happens often and thereafter, presenting a 18047 / P1639 or 18039 / P1631 or 18042 / P1634 or 18041 / P1633 then consider replacing the accelerator pedal.

No response from the throttle even with your foot flat on the accelerator pedal. There are also two redundant potentiometers in the throttle body that determines the throttle valve angle and it has three modes of failure. One for when the valve angle sensor fails, one for when throttle valve actuator (motor) malfunctions and one for when throttle valve position is cannot be recognized by the ECU. When this happens  the ECU shuts off the voltage supply to the actuator, causing the throttle valve to defaults to mechanical stop position and the engine speed is limited to 1200 RPM. If any of the DTC fault below show up in your scan, check the 6 pin plug interfacing with the throttle body. It would be best to redo adaptation thereafter before thinking of replacing the throttle body. 

000289 / P0121- Throttle Position Sensor (G69): Implausible Signal - Intermittent

16506 / P0122 - Throttle Position Sensor (G69): Signal too Low - Intermittent

17987 / P1579 - Throttle Actuator (J338): Adaptation Not Started - Intermittent

17976 / P1568 - Throttle Actuator (J338): Mechanical Failure 

17972 / P1564 - Throttle Actuator (J338): Under-Voltage during Basic Setting 

17952 / P1544 - Angle Sensor 1 for Throttle Actuator (G187): Signal too Large - Intermittent

16606 / P0222 - Angle Sensor 2 for Throttle (G188): Signal Too Low - Intermittent

000547 / P0223 - Angle Sensor 2 for Throttle (G188):Signal Too High - Intermittent

17581 / P1173 -  Angle Sensor 2 for Throttle Actuator (G188) Signal too High 

18042 / P1634 - Accelerator Position Sensor 2 (G185): Signal too High 

You have difficulty starting but eventually does start but idles very rough, bucks and surges when you attempt to drive it. The   EPC, MIL (Check engine light)  and ESP lights come on. This is most likely caused by the Injectors  N30-N33 or the Ignition Coils N (1st cylinder), N128 (2nd cylinder), N158 (3rd cylinder) and N163 (4th cylinder) since both the Injectors and Ignition coils causes exactly the same symptoms. It also   exhibit the following DTCs.

17633 / P1225 - Fuel Injector for Cylinder 1 (N30): Short to Ground  - - Intermittent

17634 / P1226 - Fuel Injector for Cylinder 2 (N31): Short to Ground  - - Intermittent

17635 / P1227 - Fuel Injector for Cylinder 3 (N32): Short to Ground  - - Intermittent

17636 / P1228 - Fuel Injector for Cylinder 4 (N33): Short to Ground  - - Intermittent

MORE EPC PROBLEMS

J757 Engine Component Power Supply Relay cause loss of  high-pressure and turns on EPC. ESP and MIL lights.

N75 Solenoid valve for charge pressure limitation and turns on the  EPC and MIL lights but shown no symptoms of failure except go into limp mode. 

Audi A1, Audi A2, Audi A3, Audi A4, Audi A5, Audi A6, Audi A7, Audi A8, Audi Q3, Audi Q5, Audi Q7, the Audi RS4, Audi RS6, Audi RS8, Audi R8, Audi S4, Audi S6, Audi S8 and Audi  TTs EPC Problems.

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.



EPC light
Epc light?
EPC light on
EPC light problem
EPC warning light?
EPC and ESP Problems
EPC and ABS warning lights on
EPC warning light, advice welcome
EPC Light and stalling
EPC what does this mean?
Epc Light that keeps coming on
EPC light and starting issues
EPC light come on frequently
EPC light pain in my butt
Epc Light On Power Loss
EPC warning light - car shakes violently - ideas?
EPC light & locked in Park. 2006 A6, need solution.
EPC light / Check Engine light - Audi not finding issue
EPC light came on and can't start the engine
EPC light coming on and difficulty starting
EPC warning light and stalling in traffic
EPC warning light is on the dash and another lamp
EPC light came on and there was lots of shudder
EPC light has just come on and doesn't go away
The EPC light came on and I had sluggish power
The EPC warning symbol came on today while driving.
The EPC warning light has been triggering fairly regularly
The warning light EPC does not go out or comes on or flashes
Occasionally the EPC light comes on
EPC Light comes on at 4000 rpm - clears on restart
EPC warning light?? 15 Nov 2011
EPC Light comes on at 4000 rpm - clears on restart 3 Mar 2011
My EPC and CEL (Check Engine Lamp) is on
My EPC light is now light on the dash
My EPC light goes on/off on a daily basis
My check engine light and EPC light is on
My Audi's epc light came on this morning
My epc light and check engine light came on
My EPC light came on then I tried to start the car but nothing happened
What is the EPC warning light?
what's the mean of epc light, when it's come on ?
When I start the car the EPC light on the dashboard stay on
when epc light's come on, car loosing power
What is epc warning light mean on a seat ibiza
Check Engine Light & EPC Light came on
When you try and accelerate the EPC light comes on and the throttle cuts out
Why does the epc light keep coming on in my audi a4
A4 with EPC light, stalling at dangerous times
Audi Q7 EPC engine management warning light
I have EPC warning light and acceleration problems
I'm having a problem with the EPC light on my 2003 Audi A4 2.0FSI
I keep getting the epc light come on
j'ai le voyant EPC qui reste allumé
Having EPC problems with a skoda fabia 1.4
Seat Leon 52 plate EPC light
Seat ibiza 1.2 EPC and Engine light on
Seat Ibiza EPC light on and acceleration problem?
Fabia EPC Light on
Seat arosa EPC light?
How do I reset a Seat Arosa EPC light?

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, 

LIMP MODE

LIMP MODE HOME / VW LIMP MODE

What is "limp mode", has been "The Question" of  2013-2014.  Limp mode is a design feature of all drive by wire systems. Vag cars fitted with ME 7.0 or newer are all fitted with electronic drive-by-wire systems in place the fast aging and outmoded cable throttle system.  Bosch ME 7.5 ECU is a very complicated system, which is torque based and makes decision based on input and feedback from all sensors needed to perform the stoichiometric calculations for optimum engine performance and torque. Failure of any of these components triggers its built-in the safety feature "limp mode" and lights up the EPC warning light. Unlike cable systems that can fray and get  stuck at high revs or high speed which often result in accidents,  "limp mode" deactivated torque and limits the revs to 1500 rpm yet allows the car to limp home safely. Many are asking, how to fix "limp mode"? The following cases are all different yet had the same symptoms - limp mode turning on the EPC warning light. The first is a Jetta, the second a Polo, the third a Seat Ibiza and the fourth a Skoda Fabia. See also  VW Polo highline, vw volkswagen limp mode,   limp home mode and  Audi limp mode.

FIRST CASE / VW LIMP MODE

Lately I've been having some issues with my Jetta 2.0T. She just suddenly went into "limp mode" or "safe mode" and it happened thrice during this week, resulting in total loss of power. I'm at my tether end, I have no idea what to do or how to rectify the situation. The first two times she went into "limp mode" the EPC warning light did not come on, however on the third occasion it came on and now stays on and  hasn't gone off since.  Initially I thought it was because the pump jockey threw-in LRP instead of unleaded fuel  but I have since rectified the situation and its not that.  I've run Vag-com diagnostics twice, which revealed the following data. I need help to repair this problem else I would have to take it to the service agents. Just the thought of a huge repair bill kept me from going there in the first place.

(First scan)
Control Module Part Number: 1K0 907 115 B
Component Version: 2.0l R4/4V TFSI 00 0010
1 Fault Found:
000818 - Knock Sensor 2 (G66): Signal too Low
P0332 - 002 - Lower Limit Exceeded - Intermittent

Freeze Frame:
Fault Status: 00100010
Fault Priority: 0
Fault Frequency: 2
Mileage: 18745 km
Time Indication: 0
Date: 2015.01.12
Time: 14:41:21

Freeze Frame:
RPM: 2555 /min
Load: 86.1 %
Speed: 52.0 km/h
Temperature: 77.0°C
Temperature: 39.0°C
Absolute Pres.: 1001.0 mbar
Voltage: 14.323 V
Readiness: 0000 0000

(second scan)
Address 01: Engine
Part No SW: 1K0 907 115 B HW: 1K0 907 115 B
Component: 2.0l R4/4V TFSI 00 0010

1 Fault Found:
000818 - Knock Sensor 2 (G66): Signal too Low
P0332 - 002 - Lower Limit Exceeded - Intermittent

Freeze Frame:
Fault Status: 10100010
Fault Priority: 0
Fault Frequency: 2
Mileage: 18992 km
Time Indication: 0
Date: 2015.01.15
Time: 12:05:11

Freeze Frame:
RPM: 2444 /min
Load: 57.1 %
Speed: 61.0 km/h
Temperature: 89.0°C
Temperature: 45.0°C
Absolute Pres.: 989.0 mbar
Voltage: 12.066 V
Readiness: 0000 0000

EXPLANATION
Our fellow VW owner is concerned with the different results of his two scans. So first and foremost let me assure him that there is nothing to worry about because the Readiness passes with flying colour. Readiness is the operational status of  the 8 emission functions, viz  the (1st nought) Exhaust Gas Recirculation - EGR, (2nd nought) Oxygen Sensor Heater, (3rd nought) Oxygen Sensor, (4th nought) Air Conditioning, (5th nought) Secondary Air Injection System, (6th nought) Evaporative Emissions System, (7th nought) Catalyst Heating and  (8th nought) Three Way Catalyst.  However, not all vehicles are fitted with all 8 system. If the system is absent, the report default to a 0 but  a 1 signifies a fault in the respective system. The RPM, load, Speed and Temperature above, are all relative to how long the engine has been running, the gradient of the road etc. The Absolute Pres of 989.0 mbar is lower in scan two  than the Absolute Pres. of 1001.0 mbar of scan one  because the battery is lower. The optimum battery voltage is 14.4V. Anyway, to get back to the "limp mode" issue at hand.  I am almost certain the cause of "limp mode" in this case is the Knock Sensor 2 (G66) because of Signal too Low - lower than expected by the ECU.  The mere fact that the ECU reports a low signal implies that the wiring from the knock sensor to the ECU is intact and that the actual fault could be the knock sensor or the ECU itself . It is highly unlikely that the ECU is at fault because they are fairly robust, which leaves us with the knock sensor. Knock Sensors are torqued to the engine block for flush contact so that it would pick up the maximum amount of vibration. Should the bolt securing the Knock Sensor come loose, the knock sensor would send a lower signal than expected. See previous blog  Knock Sensor issue. Since the ECU cannot protect the engine in the absence of knock sensor 2 it decided to enter into "limp mode" to safeguard the engine from possible damage it a knock developed or vibrations exceeded the prescribed limit.

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SECOND CASE  / VW LIMP MODE

I have a 9N - VW Polo and my car's EPC warning light comes on when I rapidly accelerate when driving at slow speeds or when accelerating rapidly while driving a steady speed. When the EPC warning light comes on, the car goes into "limp mode" at that very moment then he check engine light comes on.  I’ve scanned the ECU with VAG-COM  and after spending hours under the bonnet looking for a possible cause, I still haven't found  anything and need help or any suggestions so I can fix this problem.

Address 01: Engine
Part No: 036 906 034 FJ
Component: MARELLI 4MV 4830
3 Faults Found:

17961 - Barometric / Manifold Pressure Signals
P1553 - 35-10 - Implausible Correlation - Intermittent

17912 - Intake Air System
P1504 - 35-10 - Leak Detected - Intermittent

17550 - Load Calculation Cross Check
P1142 - 35-10 - Lower Limit Exceeded - Intermittent

Readiness: 0000 0101

EXPLANATION

The fact that the Readiness failed (see explanation above) more than explains why you are having car trouble. Since the 6th nought is a 1, it says that your  Evaporative Emissions System (EVAP) is faulty. The 8th nought is also a 1, which says that your Three Way Catalyst is at faulty. However, in your case it appears that hardware upstream of the catalytic converter is causing  the readiness to fail. The problems are associated with  Leaks Detected in the Mass Air Flow (MAF) / Intake Air System / Barometric / EVAP system . Since the incorrect amount of air needed  for stoichiometric calculations is inadequate, the fuel is not completely burnup and as a result the catalytic converter detects unburnt fuel and flags an error. The units themselves may not be faulty but rather the wiring and connectors of these units or cracks or cuts in the rubber hoses.  Repairing these should take  priority  because OBD-II is designed to shut the car down if it fails readiness and there therefore the minimum emission standards. Since the fuel is under pressure and the rubber hoses could be leaking fuel, safe mode (limp mode) is initialised.

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THIRD CASE  / VW LIMP MODE

What is limp mode? My 6L-Seat Ibiza can idle but not rev, I think it has gone into limp mode, please help before I set this cas alight. Please explain what is limp mode? And how to fix limp mode. Here is the VAG-COM scan of modules with faults,

Address 01 ----------------------------------------------
Controller: 038 906 019 NF
Component: 1,9l R4 EDC 0000SG 5839

2 Faults Found:
18043 - Powertrain Data Bus: Missing Message from A/C Controller
P1635 - 35-10 - - - Intermittent

18045 - Powertrain Data Bus: Missing Message from Electronic Load Controller
P1637 - 35-10 - - - Intermittent

Readiness: N/A

Address 03 ----------------------------------------------
Controller: 6Q0 907 379 S
Component: MABS 8.0 front H03 0001
Coding: 0000008
Shop #: WSC 06441
Note: Excessive Comm Errors

Address 08 ----------------------------------------------
Controller:
Note: Excessive Comm Errors

EXPLANATION
For an explanation of what limp mode is, read the above. The two engine faults signify there could be a problem with the Data bus Wiring since neither the Electronic Load Controller nor the A/C Controller can send and receive messages. Coupled to the fact that Address 3 - ABS braking system  and Address 8 -Auto HVAC both have Excessive Comm Errors, further verifies trouble with the  Data bus. However it is more likely Fuses and /or Connector(s) from / to Central Electronics Control and the Gateway controller. The fact that the ECU cannot coordinate torque and braking it was best to shut the systems down and enter into safe mode (limp mode) since malfunction of these important systems may lead to an accident and for the very least make for a poor driving experience.

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FOURTH CASE  / VW LIMP MODE

I have a Skoda Fabia and I think there is problems with the butterfly of my throttle body or perhaps it is dirty because the car goes into "limp mode" continually.  I have given up on kickdown because  it is getting dangerous because whenever I want to overtake, my car goes into limp mode.   I would appreciate your commentary and your recommendations because  "limp mode" frustrates me and I curse all the time. Do you think the sensors are causing all my problems? Here is my Vag-com scan.

Address 01: ----------------------------------------------
Engine
Part No: 036 906 034 BL
Component:  MARELLI 4LV       3699
Coding: 00071
 
No fault code found.
Readiness: 1110 0101

Address 08: ----------------------------------------------
Auto HVAC      
Part No: 6Y0 820 045
Component: Klimaanlage        X0760

1 Fault Found:
00818 - Sensor for Evaporator Outlet Temperature (G263)
30-00 - Open or Short to Plus

Address 09: ----------------------------------------------

Cent. Elect.  
Part No: 6Q1 937 049
Component: BORDNETZ-SG.1S30

3 Faults Found:
00906 - Horn (H1)
28-10 - Short to Plus - Intermittent

00778 - Steering Angle Sensor (G85)
49-00 - No Communications

01324 - Control Module for All Wheel Drive (J492)
49-00 - No Communications

Address 15: ----------------------------------------------
Airbags    
Part No: 1C0 909 601 C
Component: 02 AIRBAG VW51 01
 
1 Fault Found:
00532 - Supply Voltage B+
07-10 - Signal too Low - Intermittent

Address 19: ----------------------------------------------
CAN Gateway
Part No: 6N0 909 901
Component: Gateway K<->CAN 1S30
 
2 Faults Found:
00778 - Steering Angle Sensor (G85)
49-00 - No Communications

01324 - Control Module for All Wheel Drive (J492)
49-00 - No Communications

Address 44: ----------------------------------------------
Steering Assist  
Control Module Part Number: 6Q0 423 156 AB
Component and/or Version: LenkhilfeTRW        V270
Software Coding: 10140
1 Fault Found:

00816 - Power Steering Sensor (G250)
30-10 - Open or Short to Plus - Intermittent

EXPLANATION
This Skoda Fabia seems to have enough problems for half a dozen cars. Once again we need to look at Readiness first because it is quite evident that there more 1's than 0's. That tells us there are problems  in the (1st nought) Exhaust Gas Recirculation - EGR, (2nd nought) Oxygen Sensor Heater, (3rd nought) Oxygen Sensor,   (6th nought) Evaporative Emissions System  and  (8th nought) Three Way Catalyst. This is reason enough for the car to go into limp mode. But since it also has issues with its  Steering Angle Sensor (G85)
and the Control Module for All Wheel Drive (J492) there is even more reason to shut the important systemes down and do into safe mode (limp mode). There are also several electrical issues with open circuits and short circuits which would most likely be wiring harness related. But the most striking thing is the  Low - Intermittent  Supply Voltage B+ which implies the battery terminal is loose. Intermittent supply voltage  resets all modules all the time and can lead to spurious DTC.

EPC

ELECTRONIC POWER CONTROL

EPC LIGHT

The EPC fault indicator lamp is very well known among the VAG community, and for those not yet familiar with the EPC light;   it's an  amber symbol in the instrument panel displaying the uppercase letters EPC, which is the abbreviation for Electronic Power Control. This EPC lamp is often referred to by automotive technicians as K132.  EPC is synonymous to Drive-by-Wire which means that the vehicle concerned is fitted with an electrically controlled throttle valve. Restated, the old mechanical throttle cable has now been replaced by an electronic throttle control system. Vag vehicles fitted with  Motronic Engine Management version 5.9 ECUs  and older, still use a cable operated throttle interfaced with  a Throttle Control Module (TCM) and appear to be less susceptible to EPC related problems but not immune. Whereas vag vehicles fitted with Motronic Engine Management version 7.5 coupled to a Drive-by-Wire system appear to be somewhat more susceptible to EPC related problems. This is because ECUs with MEM 7.5  was specifically designed to handle the new torque-oriented  EPC function.   

However, the  bright orange EPC fault indicator light has absolutely no effect on the functionality of the Throttle Control System as a whole. When the ignition is initially turned on, it is perfectly normal for the EPC light to come on briefly,  then switch off again, if and only if it detects no Throttle Control System DTCs in memory and also determines that the TCS is working OK.  This ECU self diagnostic test takes all of 3 seconds. But, should a problem exist, the EPC light will remain on, since it needs to inform you of a DTC stored in memory  and that any additional TCS faults won't make it glow any brighter. (NB! There is no other visual way of showing you that there are several EPC errors other than with a scan tool). 

DRIVE-BY-WIRE

The Drive-by-Wire system consists of  an accelerator pedal module, that houses  two accelerator position senders, a throttle control module that also housing two position sensors,  a throttle
valve drive servo motor, an EPC light,  an ECU and of course the wiring to connect them together. 

THROTTLE CONTROL

The two accelerator position senders are a fixed part of the accelerator pedal and in reality are potentiometers. They get their supply voltage from the ECU that is capable of component diagnostics and constantly monitors its inputs. When the ECU detects that one potentiometer signal failed, it sends a DTC to the memory and turns on the EPC light then switches to the second potentiometer. It uses the accelerator pedal input voltage and translates its position  into an output voltage that drives the throttle body servo motor that controls the butterfly valve. The two throttle two position sensors, sends feedback to the ECU. Once again theses sensors are potentiometers, also monitored by the ECU and as above, if one potentiometer fails it sends a DTC to memory, turns on the EPC light then switches to the other potentiometer, but not necessarily in that order.

WIRING

The CAN Bus wire pair for the Powertrain  are Orange/Black and Orange/ Brown but there is also a supply wire (Red) and an earth (Black) wire, to each of the Drive-by-Wire components. Each of these wires have a plug and each of these plugs have at least four wires. Do the math and you could have 8 plugs - 32 male contacts pluging into 32 female contacts. The accelerator pedal potentiometers fault finding procedure.  Any of these contacts could be intermittent, all of which will cause the  EPC warning light to light up and if any of the Drive-by-Wire components fail will do the same. Considering cars drive on bumpy roads, withstand extremes engine heat and freezing temperatures at night besides rainwater that could find its way into the wiring harness. All of which could contribute to intermittent electrical connections.

REPAIRING EPC FAULTS

Repairing EPC faults are easy but needs to be systematic, because everything that can cause the problem needs to be thoroughly investigates and exonerated before the next item is suspect. Before any major or expensive components are replaced, check the wiring. Check the wiring, Check the Wiring.  Suspect the potentiometers first since they suffer from wear and tear. 

POTENTIOMETERS

A potentiometer is essentially a potential divider. Restated, its a three legged device, with a fixed high potential (voltage) and a fixed low potential (voltage)  at two of its legs. The third leg outputs a variable potential (voltage) less than the higher potential and more than the lower potential.  A potentiometer is normally made of bakelite or fibreglass with a carbon track attached to it.  The variable output makes contact with slider that runs on this carbon track. This sider/carbon contact isn't very good because its a sprung loader pressure contact. Besides when the carbon track wears through which is just a matter of time because it is constantly at work when you accelerate. It is going to give you the EPC fault guaranteed.

Feel free to upload your VW, SKODA, SEAT & AUDI scans.

EPC NIGHTMARE

EPC WARNING LIGHT

Over the past 3 years I have had some  13775 EPC information requests. That's roughly 4500 request per year, each and everyone of  them EPC related.  I manages to help several Vag car owners with their EPC problems however many were unable to give me the  DTC codes that could be causing the EPC problems. So, If you have a scan of your car feel free to upload it to my blog, I will analyse it and post the answer for everyones benefit.  I have found that the commonest EPC problem is the accelerator pedal potentiometers. However they cannot be purchased as a separate item. You have to buy the complete accelerator pedal. There is a plug that is attached to  the accelerator pedal, the plastic bit where the yellow stickers are, contains the pots.  If you are having EPC problems you are not alone. Read some of your fellow Vag car owners woes.

NO EPC DTC CODES

What is EPC on a Volkswagen? My car loses power all the time. If  I turn the car off and leave it for a while,  the problem goes away. This happened to be a couple of months ago, and  I was forced to take  it to a VW dealer.  They had no idea what to do. The car idles  really badly and the EPC light is on from the moment I start it,  besides now the check engine light is also on. I'm  thinking about replacing the throttle body but it cost about is $600. That's crazy man.

TOO VAGUE & NO EPC DTC CODES

My EPC light came on and car lost all power, so now I am having the most weirdest problems. I got stuck on the freeway, my EPC light came on and I had to pull onto the shoulder of the road because I lost acceleration. Disconnected and reconnected the negative battery terminal to reset the system, then she was driving fine. Took it to VW guy but he has no idea what an EPC problem is or at least he wanted me to  pay him  first before would help. He wants $85 an hour.

NO EPC DTC CODES, CAN'T ASSIST

I have an  VW Polo 1.4 and the 'Check Engine light' and EPC warning light  blinks for the past few months. Replaced the throttle body and potentiometer  and wiring to the engine manifold were replaced.  The same problem still persists and car  will stall at random causing these warning lights and EPC to switch on.

NO EPC DTC CODES, NO HELP

My polo 1.2  epc light comes on when I stop at traffic lights and goes into limp mode then can only drive  15 mph max without   pressing the accelerator. Took  it to a service agents who condemned  the throttle body, so had it replaced. The EPC light still comes on.

Feel free to upload your VW, SKODA, SEAT & AUDI scans.