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

VAG

VW DIY

In the not so distant pass, whenever something went wrong in your VW, Polo, Jetta, Passat,  Audi, Seat or Skoda,  you could do one of two things. Either  take it to a VW specialist to have it checked out or you could fix it yourself, if you are a hands-on, DIY kind of person. Nowadays the latter option has faded away into obscurity. With the stream of problems VAG cars are having, many of us are in the dark regarding repairs. We make educated guesses, replace parts by substitution, often costing huge amounts of money for repairs and the fault still persists. Below I have out-lined some of the problems I have encountered and with any luck shed some light on the problems you've been having with your VAG car. But before I go any further you may be itching to ask "What is a VAG car?"

Well, VAG stands for Volkswagen-Audi GMBH in Germany, also refers to Volkswagen Aktiengesellschaft or Volkswagen AG for short and Volkswagen-Audi Gelelschaft (Geleslschaft means Association). In essence, it's the same, exact and identical  group. And any car manufactured or sold by them is referred to as a VAG car. Amongst these are, VW, Polo, Jetta, Passat, Audi, Skoda, Touran, Tauareg, Beetle, Tiguan, Golf, Porsche, Amrok,  Rabbit, Bentley, Bugatti, Bora, Phaeton, Vento, Kombi, Transporter,  Lupo and the  Lamborghini, each one with a different engine with varying capacities with obscure three letter abbreviations like, BBX, AAF, AEX and APE amongst many others. However many of them have the same or similar Electronics Bosch Motronic system hardware with software ranging from ME 5.x to ME 7.x, with several support modules in common, networked to the OBD II / OBD2 (On-Board Diagnostic System ver. 2) or Can-Bus (Controller Area Network) standard.

The VW Polo 2007 with new Bluemotion technology can switch its engine off
when it comes to a halt, yet plagued by the legacy VW EPC light problem.

The idea behind this is so that only the  Volkswagen dealership technician are supposed to do the servicing and perform repairs to your car. The VW car manuals specifically discourages anyone other than qualified or trained mechanics /auto-electricians and technicians or mechanicians to perform servicing, especially changing codes and performing readiness test. Under the OBD II and Can-Bus standard, an ECU (Engine Control unit) interfaces with various other modules fitted in the car and controls and manages all sub-circuits. For example, Central Electronics Module, ABS module, Temperature Control Module, Speed-o-cruise Module, etc... When one of these modules detects a fault with one of its components, it registers a error in the non-volatile memory. Lets say you have a front wiper motor problem and it just wont work, but the fuses are OK. Even if you suspect the wiper motor as faulty and it actually is faulty and you replace it, the new wiper motor still wont work after its been replaced and switched on. You first have to clear the error or errors  from non-volatile memory with a diagnostic tool. Then and only then will it work.  

I've had the same results with my power steering which just wouldn't work after some work was done to my car and in the process the Power Steering Motor was disconnected. When it was reconnected the power steering was very stiff and difficult to steer. After going through the entire process of checking and back-tracking it still didn't work. Eventually, when the diagnostic tester was plugged in, two errors codes showed up. The first indicating that the +30V supply had dropped to an unreliable level and the second a power steering error. The first was because the battery was disconnected and the second was because the power steering plug was disconnected. After erasing the two error codes from the non-volatile memory, the power steering work perfectly normal.

I can assuredly say that I am not alone or rather that my car trouble is not unique, neither am I the only VW owner having car trouble (see previous blogs).  It appears that my 2007 Polo Classic Highline shares most of the problems listed below with my fellow VW owners. There are probably hundreds if not thousands of other  VAG car owners experiencing the same issues with their cars as I am experiencing with mine. Here are just a few of the problems that my fellow VW owners shared with me :-

"VW polo dashboard brake light stays on" / "EPC instrument fault indication light is on" / "VW polo warning lights on dashboard" / "VW  polo classic is showing epc light, starting and dying" / "polo dashboard controls" /  "VW  polo warning lights off power steering" / "warning light on dashboard" / 2007 volkswagen polo problems" / "audi electronic power control indicator" / "won't rev" / "VW Polo EPC Warning Light" / "golf mk4 dashboard warning lights" / "epc instrument fault indication" / "VW  door key problem" / "VW  polo accelerator position sensor (g79)" VW throttle body sensors"

NB! Fellow VW drivers found this site to be helpful and was interested in checking out the following sites as well.

expowp, photojani, controversy365, nerdytoys, lovelifelovehealth, sightsofcapetown, sowpbox, electroniques, blogspot-at, photo-magix, godssites, glycomix, arth-ritis, forex-bid, foodsofthecape, languagesbarrier, pimpyocar, e-gimos.

Should you find this blog informative or even help full in the very least, please recommend it to others and click on the g+ tag below. Thanks.

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.

_______________________________________________

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.

_______________________________________________

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.

WIRING HARNESS ISSUES

AUDI ON A ROLLBACK

As I've mentioned in my previous blog, not only Volkswagen  vehicles but every new vehicle's wiring harnesses have undergone a huge technological evolution since 1984. So much so that  30 years later the average wiring harnesses has become extremely complex because the number of terminals have progressively increased from a typical 200 terminals in a 1994 vehicle to as many as 1,400 terminals, if not more in the very latest models. It therefore stands to reason that with so many terminals or connections, each and everyone of them are subject to corrosion, high resistive contact, poor contact, intermittent and implausible contact  and at times no contact.  The amount of copper wire used in older cars have also decreased substantially, from as much as 4 kilometers in length to about 1 kilometer. That's equates to a 75% saving on the wiring harness.  However with all the new technology and control modules and data buses, the cost of the wiring harness  cost equates to a quarter of the cost of the entire car. 

VW Polo Wiring Harness

As can be see in the image below, another VAG car sucummbed to hi-technology and desperately needs the service centre because it went into "Limp Mode".  It's most likely an electrical fault has caused this but that's just speculation on my part. However, since more than 50% of all warranty repairs are caused by electrical malfunctions, and approximately 30 percent of all tow-ins, are due to problems associated with the wiring harness, it can be therefore be said that 80% of all troubles experienced by car owners today are due to electrical faults.  Can we then also say that these fault are constantly recurring  because the manufacturer has overlooked the fact that 1400 contacts will invariably be influenced by  bumpy roads, shaking and hoping and flexing, subject to moisture and heat and dust and dirt? Desktop computers also have several hundred contacts but the difference between household computers and cars is that computers stay in a fixed place and doesn't get knocked about and shake on bumpy roads nor subjected to extreme heat and cold and moisture. Wouldnt it be fair to say that any car with electrical problems caused by the wiring harness should be repaired by the manufacturer under warranty and if not, these cars should be recalled. Anyway,  here is the Audi scan for your perusal.

Audi on a roll back with immobilizer issues

Chassis Type: 8E - Audi A4
Scan: 01 02 03 08 09 0F 11 15 16 17 18 36 37 45 46 55 56 57 65 67 69 75 76 77
-------------------------------------------------------------------------------

Address 01: Engine Labels:
Part No: 8E0 906 018 B
Component: 1.8L R4/5VT 0004
Coding: 11701
Shop #: WSC 14385

7 Faults Found
17978 - Engine Start Blocked by Immobilizer
P1570 - 35-10 - - Intermittent
17698 - Coolant Temp Sensor at Radiator Outlet (G83)
P1290 - 35-10 - Signal too Small - Intermittent
00527 - Intake Manifold Temperature Sensor (G72)
30-10 - Open or Short to Plus - Intermittent
17536 - Fuel Trim; Bank 1 (Mult)
P1128 - 35-00 - System too Lean
18058 - Powertrain Data Bus
P1650 - 35-10 - Missing Message from Instrument Cluster - Intermittent
18043 - Powertrain Data Bus
P1635 - 35-10 - Missing Message from A/C Controller - Intermittent
16712 - Knock Sensor 1 (G61)
P0328 - 35-10 - Signal too High - Intermittent
Readiness: N/A


Address 03: ----------------------------------------------------------------------
ABS Brakes
Part No: 8E0 614 517 A
Component: ABS/ESP allrad 1326
Coding: 04275
Shop #: WSC 60690

1 Fault Found
01317 - Control Module in Instrument Cluster (J285)
49-10 - No Communications - Intermittent


Address 08: ----------------------------------------------------------------------
Auto HVAC

Part No: 8E0 820 043
Component: A4 Klimaautomat 0711
Coding: 00000
Shop #: WSC 24576

4 Faults Found
01317 - Control Module in Instrument Cluster (J285)
49-10 - No Communications - Intermittent
00716 - Air recirculation Flap Positioning Motor (V113)
41-00 - Blocked or No Voltage
00474 - Control Module for Immobilizer
49-00 - No Communications
00474 - Control Module for Immobilizer
27-10 - Implausible Signal - Intermittent


Address 09: ----------------------------------------------------------------------
Cent. Elect.
Part No: 8E0 907 279 A
Component: int. Lastmodul RDW 1010
Coding: 00011
Shop #: WSC 63351

4 Faults Found
01317 - Control Module in Instrument Cluster (J285)
49-10 - No Communications - Intermittent
00474 - Control Module for Immobilizer
49-00 - No Communications
01317 - Control Module in Instrument Cluster (J285)
79-10 - Please Check Fault Codes - Intermittent
01312 - Powertrain Data Bus
49-10 - No Communications - Intermittent


Address 15: ----------------------------------------------------------------------
Airbags
Part No: 8E0 959 655
Component: Airbag 8.4E 3001
Coding: 0011702
Shop #: WSC 63351 000 00000

No fault code found.


Address 16: ----------------------------------------------------------------------
Steering wheel

Part No: 8E0 953 549 F
Component: Lenks?lenmodul 0304
Coding: 00001
Shop #: WSC 63351


2 Faults Found
00474 - Control Module for Immobilizer
49-00 - No Communications
01317 - Control Module in Instrument Cluster (J285)
49-10 - No Communications - Intermittent


Address 17: ----------------------------------------------------------------------
Instruments
Part No: 8E0 920 900 HX
Component: KOMBI+WEGFAHRS. RB4 D27
Coding: 00142
Shop #: WSC 19411

2 Faults Found
01176 - Key
07-10 - Signal too Low - Intermittent
65535 - Internal Control Module Memory Error
00-00 - -


Address 45: ----------------------------------------------------------------------
Inter. Monitor

Part No: 8E0 951 177
Component: Innenraumueberw. 0504
Coding: 00001
Shop #: WSC 00000

No fault code found.

Audi on a rollback on the way to the clinic.

So by the looks of it, with so many error codes,  it does seem like the wiring harness could be faulty because the control module lost communications with the Instrument cluster and when this happened the checksum no longer tallied, so the immobilizer inhibited starting. But considering that the key signal was low or intermittent, it could even be that the CR1220 lithium battery in the key fob died hence could not deactivate the immobilizer. It's just so scary that your relatively new and supposedly reliable VAG vehicle could act up at any time on a lonely road and leave your stranded, so make sure you have a tow-inn agent on speed dial.


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

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.

WHY ENGINE LIGHT COMES ON

EPC LIGHT

Seeing a VW or a Volkswagen or Polo da Volkswagen or a VAG car or a new Polo on tow,  is becoming an all too familiar site, - view picture below. VW cars are seen piggy-backed and carried to service centers on a daily bases because VW owners are encountering serious trouble with their Volkswagen cars.  

Many Volkswagen drivers are often stranded on the high ways or freeways whilst driving to and from work because their VAG cars are throwing tantrums, by going into limp mode and turning on the EPC light.  Most VW drivers have no idea why engine light comes on. 

I've been late for  meetings on several occasions because of this. On a few others, I couldn't make it to the  bank in time because the Electronic Power Control -EPC- circuit incapacitated my VW Polo Classic 2.0L Highline. The worst was when I took my daughter to the dialysis clinic and the Electronic Power Control (EPC) light came on, because I ran over a speed bump a little too fast. This resulting in "Limp Mode" causing my daughter to be substantially late for her dialysis session. This could have been a life or death situation but fortunately it wasn't.

I took this photo with my cell phone. The picture quality really isn't good, so therefore the
Bluemotion badge to the left of the right side tail light  isn't clear at all.  But I couldn't pass-up
the opportunity to capture a VW Bluemotion 2012 loaded on a roll-back.

Anyway,  lets look at why this very risky and inconvenient issue haunts most VAG car owners. All Drive-by-Wire cars (since 2000) has an Electronic Power Control (EPC) light. The EPC dashboard warning lights are not exclusive to VW or VAG cars but affects most other new cars regardless of its manufacturer though the common denominator is Drive-by-Wire and an Engine Control Unit (ECU) often called the Powertrain Control Module (PCM) with an embedded microcontroller supplied by the same manufacturer.  EPC stands for Electronic Power Control which is controlled by the ECU (Engine Control Unit). In essence the Engine Control Unit (ECU) is a microcontroller with associated circuitry which control the sub-modules in the car, all connected together by either OBD II or CAN-Bus. Certain outputs from these sub-modules can activate the Electronic Power Control  circuit, especially if the reason for sending its signals to the ECU (Engine Control Unit)  could cause damage to the engine or is a danger to the passengers. For example, if the car runs out of oil, or if the emissions exceed the prescribed level, or  if  the car hits a speed bump a little to hard or if a brake bulb fails.

In the first case the oil level sensor will detect that the lack of oil in the crankcase and since there is a possibility the engine may seize-up, it sends a pulse train to the PCM to activate the Electronic Power Control (EPC), which cuts the power to the engine, making the car go into "Limp Mode" and switching on the EPC warning light. In the second case the lambda sensors on either side of the catalytic converter  will detect the fuel rich exhaust fumes and send a pulse train to the PCM to activate the Electronic Power Control (EPC), which cuts the power to the engine making the car go into "Limp Mode", thereby limiting carbon pollution and  and switch on the EPC indicator light (epc warning light) . In the third case the engine knock sensors will detect the suspension knock as the car hits the speed bump and will send a pulse train to the PCM to activate the Electronic Power Control (EPC), which cuts the power to the engine making the car go into "Limp Mode" and switch on the EPC dashboard light. In the fourth case, one of the Electronic Control Unit or Body Control Modules (BCM) sensor will sense that a brake light is open-circuit, send a pulse train to the PCM to activate the Electronic Power Control (EPC), which cuts the power to the engine  making the car go into "Limp Mode" because in that condition the car is not roadworthy. The EPC dashboard light is a very graphic demonstration that there is something amiss in you VAG that needs to be remedied.

There are several other sensors strewn throughout the car and many of them can have an effect on the Engine Control Unit (ECU) and cause the EPC light to come on. Sometimes when the EPC fault light comes on, it may be a spurious error, based on past driving cycles. A driving cycle is calculated from the time the engine starts and drives -which should be a min 5 minutes- until the engine is switched off. It could  take three drive cycles to clear a spurious error but if the fault persists it has to be diagnosed on a VAG-COM diagnostic tester.

Should you require more information on,  what is epc light, what is a epc light, vw epc warning light, vw epc code, epc on a vw, epc warning light vw, epc vw tiguan,  epc on jetta, epc light on, what is the epc light,   epc fault light, checkout epc-demystified.

Here are some Non  Volkswagen Websites I highly recommend,  

http://electroniques.blogspot.com

http://photojani.blogspot.com

http://expowp.blogspot.com