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

Automotive Electronic Components

Automotive Electronic Components

Admit it or not, we all love the new creature comforts of our modern day cars, all of which have become increasingly sophisticated.  Those seat warmers in the cold of winter, the climate control in mid summer, the air suspension on those bumpy roads, the infotainment systems with integrated GPS so that we never get lost again; and the on-board video player for those times we had to patiently sit and wait in our cars for our loved ones. ECU controlled fuel injection put an end to idling the car in the morning to get it to the appropriate operating temperature. Power steering and assisted parking makes both driving and parking a breeze. ABS and traction controls ensures that your car stops and corners without incident. 

Not to mention cruise control, the increased horsepower, the additional  safety features and the overall improved spatial comforts. And the list goes on. All of this was made possible by electronics, in the name of safety. Safety in the form of Safety Restraint Systems (SRS), Front and side airbags, early crash sensors and active front seat head restraints, to  mention but a few. 

On-Board Modules

Electronic engine management systems, carputer modules, telematic systems and other electrical components constitutes a sizeable percentage of our cars, collectively affording us the aforementioned comforts and conveniences. Besides, modern cars are loaded with code; and the number of electrical components in modern cars are on the rise, constantly and consistently increasing in number, and their failure can more often than not affect our driving safety. These electronic components can easily malfunction, either due to water ingress during wet weather conditions, or due to excessive vibration due to bad road surfaces, or just through general wear and tear. Most of these components are cheap and relatively easy to repair and replace but isolating the correct one can sometimes be trying. In a nutshell, modern day cars are seriously complicated, since they are not just computers on wheels but entire computer networks on wheels. Be that as it may, it is a well known fact that computers do crash, software have glitches and networks go off-line.

How safe is safe?

But, the million dollar question remains; are these electronic devices really safe or are they as safe as the car manufactures would like us to believe they are.  How safe is it when you're overtaking on a single lane highway at 100km per hour and the car goes into 'limp mode' or the engine just switches off and refuses to restart?  How safe is it when the steering wheel airbag explodes directly into your face for absolutely no reason? Its air pressure wave that's louder than a gun, is bound to temporarily deafen you and the smoke enveloping you would certainly disorientate you. These factors can contribute to you loosing control of the car through no fault of your own or even loose your life.  

How safe is it when you suddenly and momentarily loose steering control at high speed or whilst driving in fast moving traffic when your car doesn't react to your steering direction?  Or, how safe is it when your steering wheel suddenly goes stiff when turning (temporary loss of power steering)? How safe is it when your car randomly starts to jerk and switches off on a deserted road at night? 

How safe is your VW really, considering certain Jetta, Golf and Audi A3 models are being recalled for fuel leaks that can cause potential engine fires. Case in point, German supplier Continental Automotive GmbH has been supplying fuel tank polymer flanges that crack to five OEM parts supply companies at least 11 auto makers, VW, Audi and Porsche included.  What this means is that 
there are millions of cars of all makes and models that may have leaking fuel issues as we speak.

Electrical sub systems

As mentioned above, modern cars, can have as many as 200 small embedded electronic control units, better known as  (ECUs). Each module is in fact a fully fledged computer in its own right, overseeing one subsystem. Collectively they  have several functions, ranging from controlling the engine and or transmission, to controlling the immobilizer, to controlling the air bags, to unlocking doors, to controlling the radio, to managing the ABS, to managing the cruise control and such like. 

Most of these computer modules have input switches and or input sensors that can detect variables such as temperature, air pressure, braking, steering angle, voltages. All these computers are connected to a centrally networked  CAN bus that carries constantly varying data between them, in order to manage the car as it is being driven. The upside of this, is that the car can virtually drive itself but the downside is that when some essential module does go faulty, it would most likely shuts the car down which may also turn out to become an expensive repair.

Automakers are becoming more like 
assemblers and less like manufacturers

Essential components like headlights and spark plugs, ignition leads, wiring harnesses, relays and switches  can often be the first to go, but they are more electrical than electronic. Whereas the following list of sensors and actuators are totally electronic.

Air mass sensors (MAF) - electronic
Camshaft Position sensors - electronic
Crankshaft Position sensors - electronic
EGR Valves  - electronic
Knock sensors - electronic
Lambda (oxygen) sensors  - electronic
Throttle position sensors  - electronic
Wheel speed sensors  - electronic
Ignition Coils  - electronic
Glow Plugs  - electronic
Coolant temperature sensors  - electronic
ABS  actuators  - electronic
Injection valves - electronic
Solenoid valves - electronic
Anti-theft alarm  - electronic ... and the list goes on.

Since Automobile production requires several thousands of parts, most of these parts are not manufactured by the car maker but are supplied by auto suppliers. Hence automakers are becoming more like assemblers and less like manufacturers because Auto Megasupplier's  contributions have drastically increased from about 60% in the mid '90s to above 85% in 2017.  Among these auto megasuppliers are companies like:-

Robert Bosch supplies (Gasoline and diesel systems, chassis system controls, electronics,  exhaust gas turbochargers, steering systems, starter motors and alternators,   etc), 

Draexlmaier Group (wiring harnesses,  interior systems, cockpit and door modules, etc.),

Royal Philips Electronics (Lighting, car radio integrated circuits, liquid crystal displays, etc.)

Infineon Technologies (Microcontrollers, intelligent sensors; power semiconductors, etc.)  

Hella ( Electronic & lighting components, etc.)

DuPont Automotive (polymers, elastomers, specialty chemicals, lubricants, refrigerants, etc.) 

SKF Automotive ( Bearings, seals, clutch assemblies, SKF Automotive drive-by-wire systems, etc.) 

Valeo SA (transmissions, Micro hybrid systems, etc.)  

Magneti Marelli (Lighting, powertrain transmissions, electronics, suspension systems,  shock absorbers, exhaust systems, plastic parts, etc.)

Continental AG (Instrumentation, stability management systems, chassis systems, safety system electronics, telematics, powertrain electronics, interior modules, etc.) 

Eberspaecher Holding GmbH (Silencers, catalytic converters, particulate filters, manifolds, vehicle heaters, electrical vehicle heaters, electronics, climate control systems, etc.)

CITIC Dicastal Co.  (Aluminum alloy wheels, aluminum casting parts, etc.)

Mobis North America (Chassis, cockpit & front-end modules; ABS, ESC, MDPS, airbags,  LED lamps, ASV parts, sensors, electronic control systems, hybrid car powertrains, parts & power control units, etc.)

That being said, there are so many of these components from auto suppliers that are troublesome. For example, batteries, starter solenoids, diodes and alternator voltage regulators and relays. Considering that the alternator is the heart of  your vehicle's electrical system and that the electrical load has substantially increased due to the glut of extra electronics, I would think that some manufactures would at least have a second alternator for redundancy. Even perhaps a redundant network so that an alternative data path is  available if the wiring harness goes faulty. Or even dual temperature sensors, or dual camshaft sensors, etc. It would do marvels for reliability.

Volkswagen is recalling some 766,000 cars globally for a software upgrade to their "anti-lock braking system".

Volkswagen is recalling 8.5 million diesel cars across the European Union  due to the "emissions scandal".

Volkswagen is recalling some 90,000  gasoline powered VW Beetle, VW Golf, VW Jetta and VW Passat with 1.8T or 2.0T engines sold between 2015-2016, because the rear camshaft lobe has the tendancy to unexpectedly snap-off from the camshaft resulting in "loss of vacuum to the brake booster", implying inefficient braking and an increased risk of a crash.

Volkswagen recalls some 280,000 cars for fuel leaks.

Honda recently recalled 1.2 million  from the 2013-2016 model Accords years, citing 'faulty battery sensors'.


Ford South Africa recalled 2.0-litre diesel-powered Kuga SUVs to resolve a potential "brake problem". 

Electronic Power Control

Electronic Power Control

What Does the Electronic Power Control (EPC) Warning Light Mean?

Traditionally hand brake, accelerator pedal, clutch and bonnet release, used some sort of cable system and the steering column and gear levers used several mechanical linkages. Today virtually all these mechanical systems have been replaced by electronics in the form of sensors, feeding computers and electric motors performing as actuators. The legacy accelerator cable that controlled the throttle valve and fuel supply in the trusty old carbureter has been entirely replaced by electronics. It is now referred to as drive-by-wire (drive the car by means of electric wire control) and the EPC circuit oversees drive-by-wire system.

So what is an EPC circuit?

EPC stands for Electronic Power Control (EPC) and is a sub circuit of the car's computerized engine management system better know as its ECU which stands for Electronic Control Unit or  Engine control Unit. The EPC circuit uses the input signal supplied by the accelerator position senders and  the throttle angle senders to calculates how much engine power the driver requires. The EPC system also receives input signals from other systems on the car, like the stability and cruise control systems and translates this data into engine torque by means of the actuators.

The EPC circuit also monitors these components at start up and whilst driving and should it detect any malfunction, it will readily illuminate the EPC warning light . The EPC light is a bright yellow/amber instrument cluster light displaying the letters EPC. But it's just a 'Indicator Symbol light' that  informs the driver that an issue occurred in the torque system. Some faults within the EPC circuit will more than likely disable other functions on your vehicle that may even cause it to go into limp mode and not rev or perform very sluggishly.

EPC Warning Light

Since the EPC is a sub circuit of the ECU which supervisors several other systems on the vehicle, it is likely that other warning lights my also illuminate  on the instrument cluster. For example the Check Engine Light (CEL) may illuminate to indicate that the engine itself isn’t operating at normal efficiency. At the same time the stability and cruise control will be disabled and their respective lights may turn on as well.  

When this happens, you will need to have your car scanned for diagnostic trouble codes (DTC) or you could do it yourself if you have an appropriate scanner. Once the error codes are identified, it would be relatively easy to repair / replace the component responsible, and thereafter clear the fault codes. The illuminated lights should all turn off and the car should once again drive as per normal.

Is it safe to drive with the EPC light on?

Many people inquire  whether or not it safe to drive with the EPC light on? In my humble opinion, I would say,  Yes it is safe to drive with the EPC light on, because the EPC light is an abler light and not a red light. Red lights dictates that you shouldn't  drive the car at all, until the problem causing the red light to illuminate is repaired. Whereas an amber light is just an information sign. One can equate dashboard lights to road signs, for example if a red traffic light or a red stop sign with white-background  or other red and white regulatory sign is blatantly disobeyed, it will more likely than not result in harm or injury. Round red and triangular red road signs are warning signs and means danger. Also any sign with a white background signifies the sign is permanent  whereas a sign with a yellow background signifies that the sign is temporary and any square /diamond shaped orange/amber signs are used for roadway works information and guidance.

So return to the subject at hand, yellow/amber lights are therefore informative and temporary. However when the EPC light is on and the car goes into limp mode then its not safe to drive with the EPC light on, because you will be going dead slow and be an obstruction to other motorists. Limp mode is just a shortened form for limp home mode which is  an operating mode set by the vehicle's on-board  computer which is pre-programmed by the manufacturer. This program limits  your vehicle throttle in order to protect the engine or the car itself or its occupants from harm or injury and the car should only be driven to take it for  repairs.

As can be seen, the four signs on the right are red with the top two including white
whereas the four signs on the left are all yellow  which is informative and temporary. 

However the severity of the EPC problem can vary greatly and the vehicle may not be operable at all.  Common cause of  car’s EPC circuit malfunctioning are its sensors. Replacement normally solves the problem, however EPC faults can register intermittently to the point of frustration. In such cases it's very likely the wiring harness are intermittently faulty especially where the plugs connect to the sensors. If your engine suddenly shuts off while driving, you may want to look at the Engine speed sensor. The  crank shaft rotation sensor also commonly fail, when starting the car's engine while stationary. A tell tale sin is that the  the engine switches off after two second of idling. 

The brake light switch is yet another  EPC light trigger and is solved by replacement. This switch is a double pole double trow switch and isn't physically associated with the brake other than the same switch is used. On automatic vehicles brake switch failure locks the gear lever in Park and prevents  from selecting any other gear. The Mass air flow sensor is another common cause of EPC problems but in many cases it's not the MAF itself. It may be due to minor cracks in the rubber hoses that causes air to be sucked in, upsetting ECU calculations. The Throttle body and its angle sensors and drive motor is another is also another EPC problem child.

@volkswagenindia why am I getting EPC light again and again. Already 7 times repaired. Tired!! @Volkswagen pic.twitter.com/S1GzM6shNT

— विरल (@Viral_HS1) July 1, 2017

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

HOW TO FIX AN EPC PROBLEM - CONTINUED

HOW TO FIX AN EPC PROBLEM, - CONTINUED

The final note on the preceding blog installment ended on 'scan for Diagnostic Trouble  Codes with a scan tool'. However before we start scanning it is important to note, that Vehicles from year 2000 are fitted with an EPC (Electronic Power Control) system, hence this exposée only applies to cars fitted with a obdii 16 pin female connector, identifiable by its  normally purple core, roughly the same purple of the 6-pin mini-DIN connector  of a personal computer keyboard.  This EPC system / Drive-by-Wire circuit (implying no throttle cable) is also known as the torque circuit. The EPC system controls the EPC light  which turns on if and when there is the slightest malfunction  in the Drive-by-Wire circuit. Any such fault will more than likely generate a DTC (fault code) in the ECM, which is stored in its non-volatile memory, meaning even if the battery is disconnected afterwards the DTC (fault codes) will persist. However, also note that when the battery is disconnected all driver learnt values particular to your driving style, will be erased. Disconnecting the battery may require resetting the convenience electronics, such as alarm, interior lights and the radio. So, most importantly if you don't have the radio code, practice caution because the radio will permanently lock-up hence it's a good idea to use a jumper battery or perhaps even a battery charger to maintain battery power whilst replacing a battery. Or get the code from your service center.

Whilst any problem in the torque circuit is  normally responsible for turning on the EPC light,  the EPC light may also turn on for some other non-emission related engine faults.  When a combination of emission-related and EPC-related fault is encountered, both the MIL and EPC lights may turn on. This alone give one a good idea of whether or not the engine problem is purely torque related or part of an emission-relate issue.

Most pure torque circuit EPC faults are accompanied by Limp-Home Mode which revolve around the basic settings for the Electronic Throttle Control Valve Adjuster, Idling Control, EPC Adaptation and the  Accelerator Pedal Position Senders. Their values are stored in the ECU normally from group 60 - group 62 of the Bosch ME 7 and newer ECUs, however the actual group may vary subject to make, model and engine capacity of the vehicle. For example. Jetta, Polo, Audi TT, etc, EPC adaptation exists at group 060 - group 062, whereas these values may be stored in group 098 for some VW Passat and Audi A4, S4, B5.

Group=060, Adaptation Epc-system
Group=061, Epc-system (1)
Group=062, Epc-system (2)

Emergency Running or Limp-Home Mode

Both Bosch Motronic and Siemens Simos ECU have two emergency running modes to compensate for accelerator pedal sender failure. The first mode triggers when the primary sender G79 (Sender -1) accelerator pedal sender fails, and the second mode triggers when both G79 and G185 (Sender -2- redundant sender) accelerator pedal senders fail. In the first case with one accelerator pedal sender failing, the accelerator position is limited to a predefined value (limp mode) idling speed while some comfort functions will be disabled,  the Air Conditioner for example. By which time EPC light would have already illuminated. However, when the second emergency mode triggers the engine runs only at idle speed. It would be exactly like disconnecting / removing the accelerator pedal completely. On the occasion that I replaced my accelerator pedal, I started the engine and to my surprise it started perfectly normal and idled at a normal rev. So the conclusion is when both accelerator pedal senders / potentiometer fail, it gives you the same, exact, identical symptoms of a physical steel accelerator cable that snapped. Considering a throttle cable is the single most important part of the throttle system in a car engine. So when it breaks the car will idle, but will not rev. The EPC system mimics the pysical cable exactly or as near as dammit.

Siemens Simos ECU J361 with pin connections

Looking at the diagram for accelerator pedal senders G79 and G185, pins 50 and 19 are inputs from their respective highside driver 5V supplies with pins 18 and 45 of the ECU microprocessor are their independent internal earth connections. The two variable voltages at pins 51 and 64 are the inverse of on another. Essentially G185 (secondary) is working as a backup to G79 (primary). Inputs at pins 51 and 64 are constantly monitored by the ECU microprocessor could range from sporadic to too high or too low, to intermittent to absolutely not there. The  ECU microprocessor with its built-in Watchdog Supervision Safety Logic monitoring performing plausability checks for voltage regulation, Over/Under voltage levels, intermittent voltage levels. If for any reason that the calculations based on its internal algorithms do not correspond to its internally stored and expected values either the watchdog processor or the  Main Processing Element enable   a secondary shutdown path to all equipment under its control. In a nutshell, limp mode.

Constant movement of the gold plated contacts on the potentiometer slider eventually wears through and becomes intermittent especially if the vehicle has attained a high millage, considering  how may times the accelerator pedal has been stepped-on and released. It can be roughly compared to a volume control that's gone scratchy from constant use, when it finally worked through its carbon track and makes intermittent contact.  I've known physical  steel throttle cable to last a lot longer than its electronic counter part but they do have a tendency to fray and get stuck inside its sleeve especially when going at high speed, which is kinda dangerous -even life threatening.  With the EPC system this will not happen, rather if the "electronic steel threads fray" the microprocessor shuts the system down by switching over to its stored alternative values.

Looking at the diagram for G188 and G187 it can clearly be seen that they share a common 5v supply (pin 91) and a common earth (pin97) with the outputs from pins 90 and 92 acting as inputs to the ECU microprocessor that control for the throttle valve actuator motor. These inputs are also constantly monitored by the ECU main Processor and its companion watchdog processor. Noting once again that G188 and G187 act as angle sensors much like that of the accelerator position senders. The concept and principal is exactly the same as that for the accelerator potentiometers. When any discrepancy is detected, a shutdown path is enabled which presents itself to the motorist as a car that won't rev. Then there is G61, the knock sensor. Any  knock higher or vibration outside of that expected by the ECU on pin 102 will also enable a shutdown path and sequence limp mode. 

Accelerator 6 pin plug and harness for VW, Golf, Skoda, Fabia, Audi etc.

Accelerator Pedal 6 Pin Plug Connector Wiring Harness for VW, Amarok, Beetle, Eos,
Lupo, Polo,Touareg, Sharan, Transporter, Electronic  - 3B0 972 706

Based on this, the inputs and outputs from these three components are vital to the correct functioning of any Drive-by-Wire vehicle. So when a fault occurs and guided by error codes, it is important to ensure that there is wired continuity between these components and the ECU connector. Wiring harnesses are subjected to a fair amount of shaking and can break inside of the PVC sleeving. Especially sensitive is the 6 pin Electronic Accelerator Pedal Plug Connector Wiring Harness for VW Polo, Golf, Audi, Skoda, Fabia. VW part number - 3B0 972 706. This replacement part needs to be soldered onto the  wiring harness after cutting off the original plug.

HOW TO FIX AN EPC PROBLEM

HOW TO FIX AN EPC PROBLEM

Electronics have taken the motor industry by storm, so-much-so, that electronic black boxes and discrete components have come to replace several mechanical systems. Case in point, Drive-by-Wire system, where a mechanical cable is replaced by an EPC (Electronic Power Control) system. Or a shared coil or carburetor is replaced by a set of individual electronically controlled coils or electronically controlled injectors, respectively . As a result, providing us with increased safety features, tighter and better engine control, additional creature comforts, convenience and so much more. 

Virtually every system in the modern day car is digitally controlled by a some Electronic control Unit (ECU) or a bank of dedicated on-board computers  distributed throughout the car, all of them networked to a Central Bus System. There are numerous bus systems used in electronics but CAN bus developed by Robert Bosch in 1986, has quickly gained acceptance into the automotive and aerospace industries. With the continued development of more complex ECU applications,  much larger quantities of data needed to be  processed, scores of more signals needed to be measured, and a growing number of other parameters needed to be optimized. 

CAN bus was the answer to surmount these problems though it is essentially a serial bus protocol used to inter connect individual sub systems and sensors as an alternative to conventional multi-wire looms. In a nutshell, cars have gone electronic processors, is firmware based, software driven and data analysed, artificially semi-intelligent and electronically complex.  All of a sudden automotive mechanics needed to learn loads of new words like microprocessor, microcontroller, quantitative analysis, electronic engine-management systems, potentiometers, sensors, signal processing, frequency response, memory-mapped  let alone how their individual functions. 

To add insult to injury, abbreviations like Controller Area Network (CAN), CPU (central processing Unit), RAM (Random Access Memory), EPROM (Electronically Programmed Read Only Memory), LAN  (Local Area Network), ADC (Analogue to Digital Converter), distributorless ignition system (DIS), etc, just flooded the motor vehicle repair market. 

Talking about abbreviations, EPC, is the official abbreviation for Electronic Power Control when referring to the Drive-by-Wire Torque circuit,  though it also stands for Electronic Pressure Control when referring to the Automatic Transmission.  When the Torque control EPC circuit fails for whatsoever reason, the  EPC Warning Light (K132) located in the instrument cluster lights up, which then could cause the car to enter into "limp mode", depending on the severity of the problem. Limp mode is a protective state that the car's ECU enters into when it recognizes that there is a problem with it's logic program. 

For example, when an expected signal value originating from a sensor varies significantly from the predetermined program  specification, the ECU then enters into a secondary/ emergency programme in order to protect the engine / transmission from damage. The ECU is constantly expecting a regular stream of signal values from various sensors, like for example the Throttle Position Sensor, or the Mass air Flow Sensor, or the Engine Speed Sensor, or the temperature sensor, etc. As long as these signals stay within specified parameters for certain operating conditions, the ECU performs faultlessly at controlling the engine. 

Due to  the rapid expansion of electronics in motor vehicles, automotive mechanics in general were over whelmed by the introduction of this new evolution in technology and as a consequence didn't stay abreast of automotive electronics, thus now seem to have great difficulty in solving electronic problems on client's cars. Replacing parts indiscriminately with the hope that they get lucky and that the actual faulty component is among the suspected parts that were replaced.  

Many, many, many VW, Audi, Skoda, and Seat owners can testify to this, since most have first hand experience of taking their vehicles into the service agent, only to get the car back after having to foot an enormous bill for replacement parts that probably weren't faulty in the first place, only to discover later that the problem the car was taken-in for, still persists.  EPC problems essentially have most VW "mechaicians" by the short and curlys.  But an EPC problem is not that difficult to eliminate if checked systematically instead of trying to trace it by replacing components by substitution.

DESCRIPTION OF HOW THE EPC WORKS

When the ignition is initially switched on, the Motronic Engine Control Module (ECM) performs a quick self diagnosis of all components that are important for the correct functioning of the Electronic Power Control. If all components pass the  diagnostic test the EPC light goes out. However, should  the Electronic Power Control (EPC) Warning Light not light-up when ignition is switched on, or if a  malfunction  is detected in Electronic Power Control system whilst the engine is idling, the Motronic Engine Control Module (ECM) will turn on the Electronic Power Control (EPC) Warning Light, sort of constantly.  When this happens, a DTC entry is made in the Motronic Engine Control Module, then its time to scan for Diagnostic Trouble  Codes with a scan tool.

NB! 

EPC also stands Electronic Power Control but also stands for  Efficient Power Conversion (EPC), Emergency Power Cut (EPC), Error Protection Code  (EPC), Event Process Controller (EPC), Embedded Personal Computer (EPC), Embedded Programe Controller (EPC), Erasable Programmable Chip,  Electronic Page Composition (EPC), Editorial Processing Center (EPC), Electronic Publishing Center (EPC), Energy Performance Certificate (EPC), Engineering, Procurement and Construction (EPC), Earnings per Click (EPC), Electronic Pressure Control (EPC), Electronic Product Code  (EPC), Enterprise Planning and Control (EPC), Every Penny Counts (EPC), Earth Population Control (EPC), Enhanced Power Control (EPC), 

....To continue.....

VW LOGIN CODES

VW LOGIN CODES 

The "login" codes listed below work on many of the following Volkswagen vehicles listed in alphabetically. In order to use them you need a scan tool with the appropriate data connector plugged into your car's DLC connector.  VCDS software and its dual-K+CAN cable is probably your best option but is fairly expensive compared to the other ranges of DIY scan tools.  NB! Use these codes below at your own risk. If you don't have the necessary knowledge or expertise to make adaptation changes to your car's internal electronic module then it's best to leave them alone and refer these changes or logins to an automotive  professional, or at least someone knowledgeable about OBDII Diagnostic Trouble codes (DTC), vehicle  modules, intelligent sensors, the binary system, electronics and data link protocol transmission. These are extremely helpful if you've bee having one heck of a time trying to "login" to your instrument cluster to adapt some keys. Used incorrectly could turn your ECU into a brick so practice caution.

Dual-K & CAN Ross-Tech VCDS kit

Volkswagen:- (VW) Caddy (9K chassis) 1996 - 2003 and newer
Volkswagen:- (VW) Caddy (2K chassis) 2004 and newer
Volkswagen:- (VW) Corrado  and newer
Volkswagen:- (VW) Crafter (2E chassis) 2006 and newer
Volkswagen:- (VW) Eos (1F chassis) 2006 and newer
Volkswagen:- (VW) Fox/Spacefox/Sportvan/Suran (5Z chassis) 2005 and newer
Volkswagen:- (VW) Gol/Parati/Saveiro (5X chassis) 2000 and newer
Volkswagen:- (VW) Golf/Jetta II (19E chassis) 1983 - 1992
Volkswagen:- (VW) Golf/Jetta/Vento/Cabriolet III (1H chassis) 1992 - 1998 and newer
Volkswagen:- (VW) Golf Cabriolet IV (1E chassis) 1999 - 2002
Volkswagen:- (VW) Golf/Jetta/Bora IV (1J/9M chassis) 1998 - 2006
Volkswagen:- (VW) Golf/Jetta/Bora V (1K/5M chassis) 2004 and newer
Volkswagen:- (VW) Golf/GTI/Jetta (1K/5K chassis) 2010 and newer
Volkswagen:- (VW) Golf Variant/Wagon (1K chassis) 2007 and newer
Volkswagen:- (VW) Golf Plus (5M chassis) 2005 and newer
Volkswagen:- (VW) Golf Mk.6 (5K chassis) 2009 and newer
Volkswagen:- (VW) LT (2D chassis) 1996 and newer
Volkswagen:- (VW) Lupo (6E/6X chassis) 1999 and newer
Volkswagen:- (VW) New Beetle/Cabriolet (1C/1Y/9C chassis) 1999 and newer
Volkswagen:- (VW) Passat (31/3A chassis) 1988 - 1994 and newer
Volkswagen:- (VW) Passat (3B chassis) 1997 - 2005 and newer
Volkswagen:- (VW) Passat (3C chassis) 2006 and newer
Volkswagen:- (VW) Passat CC (35/3C chassis) 2008 and newer
Volkswagen:- (VW) Phaeton (3D chassis) 2002 and newer "facelift",  2007 - 2008)  
Volkswagen:- (VW) Polo (6N/6N2 chassis) 1994 - 2002 and newer 
Volkswagen:- (VW) Polo (9N chassis) 2002 -2010
Volkswagen:- (VW) Scirocco (13 chassis) 2008 - 2009 and newer 
Volkswagen:- (VW) Sharan (7M chassis) 1995 and newer
Volkswagen:- (VW) Tiguan (5N chassis) 2008 and newer
Volkswagen:- (VW) Touareg (7L chassis) 2003 and newer
Volkswagen:- (VW) Touareg (7L6 chassis) ( 2007 and newer
Volkswagen:- (VW) Touran (1T chassis) 2003 and newer
Volkswagen:- (VW) Transporter (70 chassis) 1991 - 1996
Volkswagen:- (VW) Transporter (7D chassis) 1997 - 2003
Volkswagen:- (VW) Transporter (7H/7J chassis) 2003 and newer


ENGINE
TDI Engine adaptation login = 12233 ( 4 cylinder MSA12 and newer)
EDC17 Security Access code =  12233  
EDC15/16 Fuel cooling Activation code =  10000 
EDC15/16 Fuel cooling De- activation code =  10001
Delete FMA Learning map  = 10008 
Switched EGR off  for next driving cycle = 10011 
DPF emergency regeneration V6 = 10016 
DPF emergency regeneration 4 Cyl  = 21295
Legal top speed limiter disable (AP07) = 28575
Teach differential pressure transmitter = 30605 

UDS Short Trip password = 27971
ME7 ECU Login Codes =  07825
ME7 ECU Login Codes = 01283
ME7 ECU Login Codes = 11500 Default coding
ME7 ECU Login Codes = 11223
ME7 ECU Login Codes = 11463
ME7 ECU Login Codes = 11501
ME7 ECU Login Codes = 12233
ME7 ECU Login Codes = 33162
Other  ECUs = 26262
Golf 1,6  FSI  = 10011 
Login codes for engine type AEL = 22158
Common Rail - disable top speed limiter = 10111
01283 Cruise Activation "older" vehicles
Activate ACC = 10002
Diesel particulate filter Adaptation  = 10016
Cruise Control Activation  = 11463  
Diesel particulate filter Adaptation = 21295
Special Customer Services login = 45678

ABS

Adaptation access  MK60 = 00212
Adaptation access  NDBW = 01025
Adaptation access  DBW = 04097
Adaptation access  SPECIAL A6 = 09399
Adaptation access  FWD = 13204
Adaptation access AWD = 13504
Adaptation access  AWD ESP = 18446
Adaptation access  MK60 = 19469
Adaptation access  FWD ESP = 23049
Adaptation access  General = 27861
Adaptation access to basic settings = 40168

AIRBAG

Airbag Adaptation Enabling login = 20324

INSTRUMENT

Instrument Cluster Adaptation Login = 13861

CENTRAL ELECTRONICS

Central Electronics Adaptation Enabling login = 21343
Activate Cruise Control Adaptation Login = 11463
De-activate Cruise Control Adaptation Login = 16167
Activate Cruise Control Adaptation = 13647  
NB! The  Cruise Control System  activation  Drive-by-Wire throttle systems will vary for different engine types.

STEERING

Steering Angle Sensor Adaptation Login = 40168

SUSPENSION 

General Login = 31564
Transport Adaptation Activation = 10273
Transport Adaptation de-activation = 41172