EPC issues

EPC Issues

EPC complaints have become the most common Volkswagen fault and outstrips check-engine-light three to one. It is one of the most tiresome and frustrating  faults to diagnose and repair because the only way of knowing that your most recent repair cured your EPC problem, is when it does't occur in the same situation under the same conditions thereafter. Mechanisms generally refer to Electronic Power Control (EPC) faults as evil, a waste of time and the cause of embarrassment.

Many disillusioned VW car owners can confirm that they've taken their vehicle to at least 2 different workshops to fix their respective EPC light problem. Often wanting a refund from the first workshop as they didn't fix the EPC issue, but only said they did. It's also known fact that tons of spare parts suspected of causing EPC have been replaced that didn't need replacing in the first place. Trial and error EPC repair seems to be the order of the day among motor mechanics. Even the agents are guilty of this and VW car owners are generally fed-up of mechanical and electronic competence. Many car owners and DIY mechanics are longing for the days when cars had a lot less electronics, were easier to diagnose and repair and one didn't need a degree in automotive engineering to replace something as meager as a MAF sensor. The word EPC among many others, is just one of the mechanical jargon that has come to invade the car industry. There are so many; to list just a few. Several of them capable of throwing an EPC light.

AIR: Air Injection System
ACC: Adaptive Cruise Control
ABS: Antilock Braking System
AWD: All-Wheel Drive
BHP: Brake Horsepower
CEL: Check Engine Light
CO2: Carbon Dioxide
CKP: Crankshaft Position Sensor
DLC: Data Link Connector
DDI: Direct Diesel Injection
DPF: Diesel Particulate Filter
DRL: Daytime Running Lights
DTC: Diagnostic Trouble Codes 
DSG: Direct-Shift Gearbox
ECT: Engine Coolant Temperature
ECU: Electronic Control Unit
EGR: Exhaust Gas Recirculation
EPA: Environmental Protection Agency
ESC: Electronic Stability Control
ESP: Electronic Stability Program 
FSH: Full Service History
FWD: Front Wheel Drive
IAT: Intake Air Temperature
KPH: Kilometres Per Hour
LED: Light Emitting Diode
LSD: Limited Slip Differential
LPG: Liquid Petroleum Gas
LWB: Long Wheelbase
MAF : Mass Air Flow (sensor) 
MAP: Manifold Absolute Pressure
MIL: Malfunction Indicator Light
MPV: Multi-Purpose Vehicle 
OBD: On-board Diagnostics
PCM: Powertrain Control Module
RPM: Revolutions Per Minute
RWD: Rear Wheel Drive
SUV: Sport Utility Vehicle
TDC: Top Dead Center
TCS: Traction Control System
TCU: Transmission Control Unit
TPS: Throttle Position Sensor
VCM: Vehicle Communications Module 
VIN: Vehicle Identification Number
VRM: Vehicle Registration Mark
WOT: Wide Open Throttle

The letters EPC in the automotive sector initially meant Electronic Parts Catalogue. Recording every conceivable component used in the  manufacture of that car, listed in alphanumeric order. Some EPC are exclusively online versions, or downloadable as pdf. Some cover specific cars  and others cover several makes of cars and is normally free, whereas the more elaborate EPCs with specialist automotive service data is charged for per search or as a monthly subscription.

For example, the ETK 2018 EPC  is specific to BMW,  Rolls Royce, Mini and the Chinese Zinoro which is the luxury automobile brand owned by BMW Brilliance specializing  in electric vehicles. ETK comes at an exorbitant price, in either downloadable or CD/DVD form. The Volkswagen  ETKA online /  ELSAWIN EPC is specific to Volkswagen, Audi, Seat and Skoda and spans 6 CDs and is also fairly expensive. It is an encyclopediac like compendium covering VW, Audi, Seat and Skoda vehicles manufactured between 1947 and 2018 in varying degrees of detail. 

It also includes the actual service & repair software used by factory technicians at Volkswagen, Audi, Seat, Skoda and their dealer workshops throughout the world. As such it would be in indispensable resource for the Volkswagen enthusiast but is also overkill for most. However most modern day cars have an EPC circuit which essentially deals with the torque of the vehicle. Using one of these catalogues and its diagnostic diagrams to identify these components and problems is one of the easiest ways of fixing EPC problems. To fix your EPC problem, click here, here or here.

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VW Beginings

VW's humble beginings

Volkswagen, derived from the German words "Folk's Wagon" or "People's Wagon," traces its roots back to 1937 when it was founded as a pivotal player in the automotive industry. Over the decades, it has grown into the largest car manufacturer globally, boasting an extensive lineup of vehicles. One of its most iconic creations is the Volkswagen Beetle, which has left an indelible mark on automotive history.

VW Beetle 1937

Commissioned by Adolf Hitler, the leader of Nazi Germany, the Volkswagen Beetle was conceptualized and designed by Ferdinand Porsche, the renowned Austrian-German automotive engineer and founder of the Porsche car company. 

The Beetle first rolled off the production lines in Germany in 1937 and remained in production until the late 1970s. However, its legacy endured, with production continuing at Volkswagen's Puebla facility in Mexico until 2003. In total, over 21 million Beetles were manufactured, earning it the affectionate moniker of the "poor man's Porsche."

The Beetle's success paved the way for other Volkswagen models, including the Type 2, famously known as the VW 'Bus' or Microbus, and the stylish Karmann Ghia. Subsequent iterations, such as the Type 3 'Ponton' and the Type 4 411/412 family car, further solidified Volkswagen's reputation for innovation and versatility in the automotive market.

Despite its iconic status, Volkswagen eventually ceased production of the Beetle, citing feasibility concerns in an increasingly competitive market. As other car manufacturers introduced similar-sized four-door vehicles, the Beetle, Karmann Ghia, and 'Ponton,' all two-door models, faced challenges in meeting the evolving needs of consumers, particularly in the taxi industry. The practicality of four-door vehicles for passenger transportation outweighed the convenience of two-door models, leading to a shift in consumer preferences.

This transition marked a pivotal moment in Volkswagen's history, reflecting the company's adaptability to changing market dynamics while staying true to its commitment to innovation and excellence in automotive engineering. While the Beetle era may have drawn to a close, its legacy lives on, serving as a testament to Volkswagen's enduring impact on the automotive landscape.

 The New Beetle was manufactured from 1998–2011 which included  a 2-door coupé/ convertible but wasn’t  a replacement for the original Beetle,  the VW golf and VW Passat was.  The original Beetle, the VW Golf  and the VW Passat were the three top VW cars in the history of the automaker, all three of which stood out for its simplicity, affordability and quality for more than thirty years.  The Volkswagen Beetle  is a two-door economy car, intended for five occupants  and sported an air-cooled rear mounted engine.

VW Fuses Switches and Relays

VW Fuses  Switches and Relays

Single Pole Single Throw

Electrical switches comes in several configurations, but are normally classified into only four types. The most common switch is the single pole single throw, abbreviated as SPST. This implies it has one contact that is normally open —abbreviated N/O—  which is closed when the switch is flicked. This type of switch is either on-or-off / open circuit or closed circuit. This switch also comes in the form of a push button switch which is normally open and closes when pushed but when released it open once again. It is also known as push-to-make, abbreviated PTM. An example of a PTM is a door bell switch or a cars hooter or the individual keys on a keyboard. Push button switches also comes in a normally closed configuration and opens when pushed, but when released, it closes again. Commonly  known as push-to-break, abbreviated PTB. An example of a PTB switch is used to release a door, held closed by an electromagnet.

Suzuki GS500 GSXR1100, Honda  VT 500 VT600 VT700 VF750,
Kawasaki ZX1000 ZX 1100 Solenoid

Single Pole Double Throw

The second and slightly more advanced switch is the single pole double throw switch, abbreviated as SPDT. This is a three terminal switch which toggles between two states when switched. SPDT are in essence two switches in one package. The one switch is normally open whilst the other is normally closed. By flicking the switch the two switches reverses their roles. The normally open switch is then closed and the normally close switch is opened. By connecting a SPDT at either end of a long passage to turns the lights or off, one is able to enter the passage at one end, turn the lights on and when exiting the passage at the other end switch the lights off. SPDT can be used as a SPST in an application by just using the centre contact and either one of the other two contacts, depending on what type of switch you need, N/O or N/C.  SPDT switches are also available with a centre-off position, known as momentary (ON)-OFF-(ON) switch.

Volkswagen 4H0951253 Starter Relay 645 and 1J0906381A Fuel pump relay 109. 

Double Pole Single Trow

The third type of switch is the DPST and is similar to the SPST switch in operation except that it has a pair of on-off switches that switch together. It is commonly used to connect / interrupt both the live and neutral supplies in a circuit simultaneously or it may be used to switch two separate circuits simultaneously. Computer power supplies have DPDT switches as a safety feature to avoid getting electrocuted whilst working on the power supply if only one pole was switched. 

Double Pole Double Throw

The fourth type of switch is the DPDT and is similar to the SPDT switch in operation except that it has a pair of on-on switches that switch together. It is commonly wired to reverse the direction of a DC motor or be used to switch between to different colour LEDS. DPDT can be used as a DPSP in an application by using the centre contact and either one of the other two contacts and duplicated on the paired switch. DPDP switches are also available with a centre-off position, known as momentary (ON)-OFF-(ON) switch.

Switches 

Switches switches come in various shapes among which are Toggle switches, limit switches, reed switches, micro switches, mercury switches, rotary switch, slide switch, rocker switch, pneumatic limit switches, selector switches and getting the right switch for the job cam sometimes be tricky and may be better suited by using a relay. Many switches also come with a rubber jacket to make it  waterproof. However that doesn't imply you can submerse the switch in water, it is more a splash proof cover than a water proof one. There are switches suited for using under water, for example a floating mercury switch. when a vat or tank is filled with liquid, the switch would float in the upright position but when the liquid falls below a certain lever  the switch would float upside down and trigger. Perhaps turning on a pump that would fill the tank or vat once again.

Whats a relay?

Having discussed switches you may ask what does switches have to do with relays. The simple answer is, a relay is essentially a remotely controlled switch. Relays are controlled electrically rather than mechanically, hence they're known as electro-mechanical relays. They are commonly used in automotive design, where high current devices can be switched from a cockpit fairly cheaply. In stead of using long lengths of thick high current cable and a substantially heavy duty on-off switch to control a heater or a motor situated some distance from the driver; a small low current switch and a length of thin low current cable and a relay switch with heavy contacts would suffice. Every relays has a solenoid configured as an electromagnet. So when the solenoid is activated by a trigger voltage, the electromagnet pulls a set of heavy duty contacts to make or break a circuit. Relays are versatile and can function as a simple spst switch, or a more advance spdt switch of a dpst switch or a dpdt switch depending on the circuity it needs to control.

Volkswagen Solenoids

Sometimes you may need a switch with more contacts than the best switch you can find, and this is where relays outweigh switches. Relays also cost less than the combines cost of all the switches that it replaces or that can do the job of.  Volkswagen have several relays throughout its electrical system and the most hardworking relay, is the starter relay.  Starter relays form part of the starter, the reasoning, is to keep high current conductors as short as possible. However many cars have a second relay inserted into the fuse panel that powers the starter solenoid. So when you turn the ignition key to start your car, the starter relay contacts in the fuse box sends 12V to the starter solenoid on the starter. This solenoid's contacts throw and sends 12V from the thick battery cable that's connected to one side of the starter solenoid directly to the starter's field coils, causing its armature  to spin. But at exactly the same time the solenoid performs a dual function as it kicks the bendix forward into the ring gear's teeth.  The starter's force of rotation is sufficient to crack the engine and if all's well, the engine with start. 

Volkswagen

Volkswagen

Volkswagen cars are extremely popular. In fact, they are so  popular that Volkswagen as a brand is the favourite car of many South Africans, besides being the most popular car sold on the South African market. Volkswagen cars are also popular elsewhere and are sold in virtually every country throughout the world; but its popularity and its global acclaimed robustness doesn't make it indestructible. 

Volkswagen cars give problems, in fact they are more troublesome now, than they've ever been. The reason, the ODB-II system with its ever increasing number of ECUs.  This system has several features that means well, like controlling toxic emissions, like giving you the best fuel efficiency;  and is capable of detecting minor issues or glitches before they actually occur, among so many other beneficial features.

However, like every coin has two sides, and as there are always two side to every story, there is also a reaction to every action.   Meaning for every beneficial feature of OBD-II there is a detrimental feature to OBD-II. OBD-II is essentially a computer system with a host of additional computer modules remotely placed through the body of the car, some of which have an effect on the Engine ECU. 

These modules or sub-ECUs oversee various features, like an airbag controller module/ECU that supervises the airbag. This module is connected to crash sensors placed in strategic positions in the car, that triggers when a crash occurs and ensure that the airbag is inflated within the required time frame. Then there is also an immobilizer module/ECU that supervises the starting process ensuring the correct code from the key transponder chip corresponds with its randomly generated code. There is also an ABS Brakes module, a Gateway module, a Steering Assist module, an Instrument Module, a Central Convenience module, a Radio module, to mention but a few. All of which are potentially sources of problems.

If we only look at the Airbag and the Immobilizer modules/ECUs, both will impede driveability and the starting of the car, by influencing the Engine ECU. If the Engine ECU doesn't received the expected signal from either, it would refuse to start the engine. The Engine ECU is the heart of the ODD-II and normally sits in the engine compartment or inside the car under the dashboard. All three these modules/ECUs mentioned, sometimes also referred to as nodes, are in within a meter of on another but here's the downside. 

To get them to sing in harmony they are connected together by a wiring harness. This wiring harness plugs into each and every node in the car, and also share a common twisted-pair wire-connection  called a bus which is terminate at each of its ends with 120 Ω resistors. This bus can be either Controller Area Network (CAN) or  Local Interconnect Network (LIN) or even FlexRay. Each module also has a power supply and an earth connection. All of these wire connections are potentially sources of problems.

The average car can have anything between 5 and 100 modules/ECUs, some ECUs have as few as six connections and others as many as 80 or 94 or even more. Each of these physical connections are prone to corrosion, metal fatigue and physical flexing due to suspension vibration and is a source of future problems. Some ECU's earth connection is solely made through body contact and if it looses contact due to vibration or water ingress, it will undoubtedly cause an error or errors. 

These errors are stored in the ECU's non-volatile memory which can at times be quite cryptic. I can say that without doubt that every "automotive technician" has misinterpreted DTCs and replaced unnecessary components in the process. Even returned cars to the owners claiming that they solved the problem but didn't, they were just under the misapprehension that they did.

If any connection out of this glut of connections becomes intermittent for some reason or the other, it would be like trying to find a needle in a haystack and there are so many "automotive technician" that have never touched a needle nor even seen a haystack, let alone find a needle in a haystack. Be that as it may, one of the advantages of OBD-II is that it increases the likelihood of a DIY fix, providing the fixer is fairly dexterous and have some electronic and mechanical knowledge and have access to a diagnostic scanner.

A fairly common plug connection that goes intermittent, is the one that connects to the throttle body. It supplies the voltage to the stepper motor that controls the throttle butterfly valve. This plug also sends feedback to the ECU so that it knows how wide open or close the valve is. So many mechanics insist on stripping the throttle body due to a throttle body DTC and claim after cleaning it, the problem was solved. However a few days later the error would be back. A word of caution, Don't suspect replaceable parts especially if it has less that 100 000 km on its clock. Exhaust the possibility that it's a possible wiring harness problem before replacing expensive items because they can never be returned to the agents after its been installed.

Another intermittent connection it the 6 pin plug that interfaces with the accelerator pedal. This is a common source of the dreaded EPC problem. In many cases, a squirt of electro cleaner may solve this problem. That's to say until it's triggered by something else. It's worth while to check the voltage supply stability and ground impedance between the 6 pin plug and the ECU. Remembering that the pedal's earth connection is grounded inside the ECU and the ECU is grounded to the body or chassis and not the engine. In some cases, the ECU will function normally because its metal casing is not earthed.

Also, don't be tempted to earth the pedal earth directly to the body when there is a  significant resistance reading. Rather replace that portion of the wiring harness that may have gone high resistive. Offset ground connections and ground loops can cause voltage drops and magnetic impedance which are major causes of noise hum, and interference in computer systems (ECU). So don't alter the the existing ground connections because it could introduce issues you've never experienced before.

What does it mean if the EPC warning light comes on in a Volkswagen?

What does it mean if the EPC warning light comes on in a Volkswagen?

Since the inception of the motor vehicle, several manufactures have claimed that their brand of car, has sold the most units globally. But since there is no definitive comparative yardstick to measure the exact amount of units sold,  Volkswagen claimed that their Volkswagen Beetle is the "bestselling car in history", considering they had sold more than 21 million units. To be more exact, The New York Times, date July 31, 2003 stated that the very "Last Volkswagen Beetle" manufactured was in fact number 21,529,464. 

Ford on the other hand manufactured their 1 millionth Model T's during the last month of 1915, with total sales of 15 million units produced by 1927 when they ceased production. In 1972 Volkswagen broke Ford's record when their 15,007,034th Beetle came off the production line in Puebla, Mexico. 



Be that as it may, Toyota boasts that in reality, their Toyota Corolla is the "bestselling automobile in the world", after reaching their 40 millionth unit in July 2013. But regardless of their claim, Volkswagen is undoubtedly still the "bestselling automobile in the world" seeing that the Volkswagen Beetle didn't change its shape or form since 1945 up to and including 2003, whereas Toyota used their Corolla label for eleven generations of Toyota cars, built since 1966 and this very Corolla label is still in common use. Non-the-less, statistically Volkswagen has been the best selling car globally until late 1998; meaning the Volkswagen Beetle remains the "bestselling vehicle ever". 

Enter the Volkswagen Kombi, Volkwagen City Golf, Volkswagen Fox, Vokswagen Jetta, Volkswagen Golf, Volkswagen Polo, Volkswagen Passat, Volkswagen Kombi, Volkswagen Sharan, Volkswagen  Toureg, Volkswagen Amrok, Volkswagen Transporter and the list goes on. However this entire Volkswagen fleet doesn't come without their fair share of  problems. The most common of which is probably the EPC light accompanied by limp-mode home.

What is the VW EPC Warning Light, 

The Electronic Power Control warning light, is commonly known as the EPC warning light. It's a dashboard warning indicator that suggests that there may be a problem with your Volkswagen’s throttle system. The throttle system consists of the accelerator pedal, the throttle body, traction control, cruise control, and the ECU, which is collectively called the drive-by-wire system. 
The drive-by-wire system is also sometimes referred to as an Electronic Throttle Control (ETC), roughly described as a technology that electronically "connects" the accelerator pedal to the throttle, instead of a mechanical linkage. 

In a drive-by-wire system, an electric stepper motor determines the angle of the throttle valve. How wide it opens or closes, is calculated by a —closed-loop control algorithm— software controlled embedded system built into the ECU. The ECU makes decisions based on various input data from several sensors, among which are, the accelerator pedal position sensors, engine speed sensor,  vehicle speed sensor, and the cruise control switch. The Electronic Control Unit (ECU) can also be described as a computerized ignition / engine management system  that operates in conjunction with the stability and cruise control systems. When the EPC light comes on, it means the problem is not emission related, whereas the Check Engine Light (CEL)indicates emission related problems but when it lights up, can be accompanied by the EPC light. If the EPC warning light comes on in your vehicle, it is important to have it seen to as soon as possible, because it you don't invariable it's going to trigger again when you least expect it.

EPC Car Warning Light

When the EPC light comes on in your Volkswagen, its throttle may be limited in power, yet have sufficient power to drive the car to a dealership or mechanical workshop, but it shouldn't be driven elsewhere. This is called limp-mode-home. Limp mode home is  inherent in its the software design in order to to protect the car from run-away and  its passengers from possible injury. Volkswagen cars equipped with a Electronic Stability Program (ESP) program, will display its ESP light instead of the EPC light and may automatically trigger the car into limp-home mode. 

Vehicles fitted with Traction Power System (TPS) are also prone to enter into 'limp-home-mode'  which effectively prevents software glitches from initiating or activating unintended acceleration.  In 2011 the U.S. National Highway Traffic Safety Administration (NHTSA) commissioned a team of NASA software engineers to evaluate software of late model year Toyota and Lexus vehicles, alleged to be the cause of  unintended acceleration collision, which caused the death of a passenger in a September 2007. 

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The Definitive EPC Guide 2

The Definitive EPC Guide (Continued)

For part ONE Click Here!

Having said that, in my humble opinion, the  EPC circuit with its drive-by-wire circuit and its "Limp-mode home" mode, is a value-add for modern car design; and though frowned upon by many, is a very valuable safety feature. Also bearing in mind that when the communication network is momentarily unavailable and an application that depends on it is unable to communicate, it may trigger the ECU into "Limp-mode home" and set a DTC. Exception errors do occur in  synchronous or asynchronous distributed system, where software entities act as clients or servers or both. So when where 1...n clients are requesting services via a specific protocol from typically one server; the server services the client  but  temporarily blocks its service request and data flow control, whilst other client expects a response from the server.  

If 1 client to n server communication can be established, it would certainly solve the problem but it’s currently not supported. Also remembering that the CAN bus is a serial communication network through which all modules communicate with the ECU via a Central Gateway, some uses FlexRay frames and others Lin bus or CAN, each with a differing topology, some synchronous and others asynchronous. The Central Gateway is responsible for frame or signal mapping function between two communication systems, like from LIN/MOST/CAN/FlexRay to Ethernet transport systems. However ECU gateways often have two or more internal Gateways like the Service Data Unit (SDU) gateway, Layer 3 Tunnelling Protocol (L3TP) gateway and the Signal Gateway needed for frame or signal mapping function between two disparate communication systems.

The best analogy with which to explain the above would be your cell phone. Cell phones are native Global System for Mobiles (GSM) devices with a microprocessor and its support chips, much like the automotive ECU. Cell phones support the Hypertext Transfer Protocol (HTTP) and the Wireless Application Protocol (WAP) for Wi-Fi as well as the Bluetooth communications protocol through a "Gateway" which translates it to a common data stream native to the Cell phone operating system. 

So, while you’re downloading an email and the phone rings and you answer; the email download temporarily stops but will resume when the call is terminated. The same applies to a Bluetooth file transfer which will be interrupted even possibly terminated when a phone call is answered. However, not all services are prone to such interruptions because some services are inherent to the design. For example, when you’re listening to music on your cell phone and you answer an incoming call, the music is temporarily suspended until the call is terminated then the music will resume. 

This function is purposely part of the design whereas exception errors are not and are more prone to happen with asynchronous communication, caused by propagation delays. This is what also happens when the ECU inter communicates with other modules and when the messages are not delivered within a prescribed period of time, can cause the car to go into "Limp-mode home" . So if for some reason the radio that is a non-essential service is hogging the network bus, and you step on the brake which the ECU will undoubtedly detect but the brake light didn't illuminate within the expected response time, which the ECU will also detect, then the car may go into "Limp-mode home" . 

Or you could hit a speed bump in the road at high speed and bounce back onto the road; the thump if hard enough or loud enough to trip a knock sensor would cause the car to go into "Limp-mode home" . Or you could have just done some high rev spirited driving to cause the car to go into "Limp-mode home" . One consolation is that, when the ignition is initially turned on; right before the car is started the ECU does a self-test to verify that all’s well, and if that is the case, the car will start and drive normally. 

However, if the self-test fails, one of the caution lights may remain on. It could be either the EPC light or the Check Engine light or perhaps both, or one or both could be blinking, which is a sure sign that you may have a problem. Once again, a diagnostic scanned would be the most informative way of establishing what the problem is. But I’ve encountered car owner who took their vehicles for diagnostic tests and no errors were flagged, so in some cases may be a futile exercise. 

Having said that, if you are stranded along the road side, the best would be to reset the ECU by removing the battery earth terminal for a minute or two, but make absolutely certain that you have access to your radio / DVD code before  you disconnect. Whatever errors occurred prior to this will be safely stored in the ECU non-volatile memory and may be checked when a diagnostic scanner is available but all stored values will be lost.  The downside of doing this, is that an additional error would be flagged because the battery (+30V) supply was interrupted, and now the ECU has to relearn your driving style.

ECUs are fairly robust and are more-likely-than-not the cause of your EPC problems, though unlikely but not impossible.  The most likely component in my humble opinion that would cause constant and annoying EPC problems would be the wiring harness. Not the actual wires, unless they are frayed and damaged by rubbing against the chassis but rather its edge connectors. 

The ECUs and associated modules each have multi-pin connector that’s tin plated and can become intermittent due to the constant vibration of the car. Copper contacts also oxidizes fairly quickly, so to prevent this from happening, they are tin plated which provides for a low resistance, good contact surface. However when water enters this connection, especially in the presence of a voltage or current flow, the contact normally turns black or corrodes green, impeding continuity hence connectivity. 

A poor vehicle ground connection is another culprit that can intermittently trigger the EPC light without leaving a DTC.  A blown tail light / brake light bulb can also cause the EPC light to turn on without leaving a DTC. Always make sure that the replacement is a 12V 21/5W bulb because the wrong bulb will also cause the EPC to trigger also without leaving a DTC.  A faulty brake-light switch (DPST) is also commonly known for triggering the EPC light and sometimes causes the 10A fuse to blow. 

So, when the brake is applied and the switch throws, its contacts reverse, meaning the normally-open contact closes and the normally-closed contact, open. If there is a delay in the switching time, even as short as .5 of a second, the EPC light will trigger, without leaving a DTC.  A tell-tale sign that the brake-light switch is faulty or that the fuse is blown; is that the Cruise Control appears to be faulty. Since they are both interconnected, the Cruise Control is reliant on a voltage provided through the brake switch. 

DTC can often be intermittent or sporadic so it’s best to ignore those, in preference of repairing those that are permanent. In so doing, they may have interrelations and the sporadic ones may disappear after the permanent errors are fixed. So, it’s best to perform a diagnostic scan, preferably an autoscan with VCDS first, then delete all DTC in the process. Thereafter save this scan and printout a hardcopy to store with the vehicles registration papers. 

The importance of this printout is that it’s a reference to all the modules coding, and if something is inadvertently changed, there would be an unalterable record to refer to. Once done, and as mentioned above, disconnect the battery's negative terminal then disconnect the positive pole and place the battery on charge for about two hour.  Replace the battery by first connecting the positive pole then lastly the negative pole.

 By following this sequence you will prevent damage to the electronics modules strew throughout the car.  At this point, all pre-learnt and all stored values would have been erased from the ECU. Essentially all the control modules would have been completely reset, restarting with a clean slate.  After starting the engine and driving the car for a short distance, check to see if any DTC have been flagged.

Resetting an ECU occasionally is a good thing, because any and all electronic equipment with a microprocessor can experience an unrecoverable error or an internal parity error or fail a cyclic redundancy check and requires a "cold" system restart. Computer  memory (RAM) also experience memory read/write errors, interrupt or address errors and general protection errors; so  when the ECU is reset/cleared, along with its non-volatile memory, the memory (RAM) is also reset.  AUOTSAR and its core partners are trying their utmost to rectify such problems in automotive ECU, but until they do, we will have to contend with EPC problems.

To read the first part... click here.

The definitive EPC guide

The Definitive EPC Guide

The following is the definitive guide to the Electronic Power Control (EPC), but before we continue, let me expound on what this guide is and what it's not. The very purpose of a guide is to provide information; to aid, give direction, to grant assistance, to facilitate, to support and to help you towards a solution or provide you with an explanation or an answer. However, even though this guide may furnish you with several answers, not every question can be satisfied by the same answers, though it could possibly steer you in the right direction. Hopefully you'll find this EPC guide definitive enough to provide you with the necessary knowledge to fix your Volkswagen, Audi, Seat or Skoda's EPC problem. Or at the very least, steer you in the right direction or share the lingo with which to discuss your EPC problem with your mechanic. 

But before I continue, let me first explain what EPC is. EPC stands for Electronic Power control and is a subsection of the OBDII. OBDII sometimes writen as OBD2 stands for On-Board diagnostics 2, which is composed of mandatory equipment installed in every motor vehicle manufactured since 1996. The purpose of this real time OBDII system is to control harmful exhaust emissions, by rigorously controlling the moment of combustion as close to the Stoichiometric  ideal as possible. Stoichiometric combustion is therefore controlled by an ECU (Electronic Computer Unit) in conjunction with the mass air flow components and the lambda oxygen sensors through constant feed-back in order to increases or decrease the short term fuel trim.  

To define an ECU instance, one could say that it consists of one microcontroller with its peripheral chips and its configured  software application.  This also implies that if more than one microcontroller in packaged in the same ECU housing, each microcontroller requires its own description of said instance. As such, each ECU forms an integral part of the OBD2 system, with strong interaction between hardware sensors and actuators; constantly monitoring and controlling several other engine components to provide the best engine performance at the most efficient fuel use , as well as provide the driver with the best driving experience. Another part of the OBD2 system is its network bus which interconnects several distributed computerized modules, ECUs, sensors and actuators, collectively geared towards better functionality and passenger safety. But before I get carried away, let me return to EPC.

The EPC sub circuit when triggered turns on the EPC light or LED which displays the letters EPC quite brightly in the display console. Many VAG car owners have asked “What's the meaning of EPC warning light when it comes on in a Volkswagen"? Short answer; it’s just a caution light like any other warning light, drawing your attention to a possible problem but with one exception. This exception is that the EPC light is an amber/yellow light and not red. 

Much like road signs that have different colour boards for danger/warning than for  prohibitory/restrictive signs  or than for  service/information  purposes, the automotive sector uses, red lights to signify danger/warning which warrants immediate attention and amber/yellow lights for informative/attention which also requires your attention, though not immediate. When the ECU detects that the engine oil is low for example, it turns on a red light – red oil-can image – which implies that it's dangerous to drive the car in that condition because its engine could seize and therefore begs you to respond and remedy this situation immediately. 

Likewise when your handbrake in engaged, a red light – red disk with a P or exclamation mark inside –  is displayed, implying that it's dangerous to drive with the handbrake engaged, expecting you to release it immediately. Disregarding this red light and driving the car with the handbrake engaged could cause the brake pads to overheat and fail to function when needed but that’s to say if the car would even move from its stationery position with the brake engaged. Headlights on the other hand are indicated by a green dashboard light or a blue dashboard light when the Brights are switched on, neither implying danger nor attention. So in that sense, the yellow EPC light is just an attention light, much like the yellow safety-belt-light provides information that you haven’t bucked up or the yellow reserve-fuel tank-light informing you that you would have to add fuel shortly.  

Very importantly, a yellow light doesn't mean disregard, because disregarding a fuel tank yellow light could leave you stranded without fuel along the roadside. Or disregarding the yellow seat belt light could result in a traffic fine for non compliance to traffic laws. Therefore do not disregard the yellow EPC light and have the possible problem seen to at your earliest convenience. I hear you asking “What can I do when the Yellow EPC light comes on"? Normally when the EPC light comes on, it is accompanied by "Limp-mode home" and sets a DTC in the ECU non-volatile memory. So you need to have your car scanned with a diagnostic tester to determine and analyse the DTC error. 

I hear you asking "What is limp mode". Short answer, when the ECU detects a problem in the toque circuit it prevents the engine from revving above 2000rpm. In effect, it limits the electronically controlled throttle valve – Drive-by-wire – from opening wider.  “So what’s this Drive-by-wire thing”? you may ask.  Well the drive-by-wire circuit is a sub circuit of the EPC circuit and it simulates an accelerator cable, where the depression of the accelerator pedal is monitored by the ECU which in turns drives the throttle body valve open, in unison with the pedal action without any physical cable connection. Essentially it's an electronic version of an accelerator cable /acceleration process. Its electronic circuit is composed of dual sensors constantly monitored by the ECU, and any interruption in its data, will more-likely-than-not trigger "Limp-mode home", turn on the EPC light and set a DTC.

The ECU also constantly monitors the dual sensors in the throttle body as well as  the motor that drives the throttle body butterfly valve. Any interruption in its data will more-likely-than-not trigger "Limp-mode home", turn on the EPC light and set a DTC. This is a safety feature built into OBD2 to prevent the car from going into runaway mode with the possibility risk of injury. Image what would happen when a frayed accelerator cable jams inside its armoured sleeve, unable to decelerate the engine whilst travelling at a speed in excess of 72kph. Considering more than 50% of all accidents in rural areas happens at speeds between 72kmph and 80kmph whereas 70% of all fatal crashes on the freeway occurs at speed of 100kmph or higher.

Continue to part TWO.... Here!

AUTOSAR and the automotive black box.

AUTOSAR and the automotive black box.

Within the next few days the 11th AUTOSAR Open Conference will be hosted at the Portman Ritz-Carlton in Shanghai China. The date of this event is scheduled for the 6th - 7th November of 2018 and that's a mere 8 days from today. At this conference AUTOSAR experts from within the automotive industry will present their  "Future Automotive System Architecture", both  the  Classic and the Adaptive Platforms. Both specifically developed to support high performance microprocessors, with improvements in the safety and security demands for autonomous driving vehicles, aka self driving vehicles. Essentially all motor vehicles of the future.

AUTOSAR logo

They advocate that, due to the latest connectivity requirements and the enormous possibilities available through the “Internet of Things” it is mandatory to upgrade the current system architecture of automotive electronics. Especially when considering their new applications like advanced driving assistance, electric mobility, autonomous driving, V2X (vehicle-to-everything communication) and off board connectivity over the air (OTA).

So what does all this mean in layman's terms. Well, it is AUTOSAR's attempt towards automotive standardization and for the development of smarter, safer and more secure vehicles in the future.  So, who is AUTOSAR you may ask? The short answer; AUTOSAR stands for (AUTomotive Open System ARchitecture) and is a worldwide development partnership of over 250 vehicle manufacturers, suppliers, service providers and companies from the automotive electronics, semiconductor and software industry. Their collaboration  and  collective objective is to agree on a "Standardized Software Framework for Intelligent Mobility" and implement it, as the way forward. 

An incomplete overview of the AUTOSAR Runtime Environment
and how components plug into it

This would simplify replacement and updates for software and hardware, which essentially forms the foundation for reliably controlling the growing complexity of electronic and software systems in today’s and future vehicles. The AUTOSAR alliance was formed in June of 2003 and comprises of  9 "Core Partners"  viz, BMW Group, Volkswagen Group, Continental, Daimler, Ford, General Motors, the PSA Group and Toyota. In addition there are some 43 Premium members as well as another 112 associate members collectively contributing to the motor industry.

Standardization is a good thing and when coupled to "open architecture" is even better. Case in point, Linux is open source and it revolutionized computing.  Linux was selected for its ability to run on many and various makes and models hardware boards. Besides, Linux more-likely-than-not has the widest device driver support of any other operating system on the planet. As such,  Linux became the de facto application software for developing specialized embedded devices in consumer electronics. For example, personal video recorders (PVRs), wireless access points (WAPs), personal digital assistants (PDAs),  Global positioning systems (GPSs), in-vehicle infotainment (IVI), routers, switches, set-top boxes, navigation systems, home automation systems, car dashboard sytsems, security appliances, etc. 

Linux is such a highly flexible platform that makes it relatively easy to port to other hardware architectures. As such Android relies heavily on its level of hardware abstraction (HAL). Android is an open source Linux-kernel-based operating system which revolutionized handsets far beyond phones, tablets and TV's. When Google acquired Android, they created the Compatibility Test Suite (CTS), which defined what OEM's handsets should comply with, to be Android-compatible.  This CTS is just just a HAL (hardware abstraction layer) for the Android stack. 

In the same vane AUTOSAR intends an open and standardized software architecture for automotive electronic control units (ECUs). It's RTE will act as a HAL sitting on a layer between the application software and the Hardware.  It would form a standard ECU (black-box) usable by all manufactures with a layered software architecture that would reduce individual expenditures for research and development while mastering the growing complexity of automotive electronics. 

The AUTOSAR operating system is also backward compatible with OSEK/VDX (ISO 17356) and consists of Basic Software Modules, Application program Interface (API), Specification of ECU Configuration Parameters (XML), Standardization Template, Generic Structure Template, Interoperability of AUTOSAR Tools.  Hopefully the AUTomotive Open System ARchitecture would do for cars and safety in general what both Linux OS and Android OS have collectively done for consumer electronics as a whole.

My EPC light came on

My epc light came on

Virtually every  motoring enthusiasts who owns a Volkswagen Golf TDI  simply loves its torque; its drive, its racy performance, its braking, its fuel economy and especially its manual transmission model. Be that as it may, 6 out of 10 Volkswagen and Audi owners are unhappy about Volkswagen as a whole. Unhappy about their cheating devices, unhappy about the emission scandal, unhappy about the entire VW TDI buy back claims processes, but more specifically unhappy about having to give back the car that they love so much.

According to the 225-page court document that outlines VW’s settlement, which reads,

“At the present time, there are no practical engineering solutions that would, without negative impact to vehicle functions and unacceptable delay, bring the 2.0 Liter Subject Vehicles into compliance with the exhaust emission standards.” 

This is so wrong on so many different levels hence most VW and Audi owners are completely pissed-off -pissed-off at Volkswagen. Event hough most VW TDI enthusiasts haven't returned their cars, they are already missing them, even before it's taken back; all of them very unhappy about it. It's always good to be optimistic about the buyback outcome but pessimistically speaking, VW, Audi, Seat and Skoda owner's are all complaining about their cars, ranging from, 

"My epc light came on and I lost power",  to 

"I got stranded on the side of the highway today for  almost an hour when my EPC light went on",  to 

"The first time it happened, the EPC light turned on and loss of  power lasted for a day and then it went away on it's own",  This is now the third time this happened, the EPC light comes on and then my car just loses power", 

"I took my car to the VW agents for a EPC problem who then said they  found a few error code but they didn't know what was wrong, so they just reset them",  

"Totally disgusted, by the dealer's complete and utter  disregard to accept responsibility for their pathetic  workmanship. They threw a dozen parts at the problem at my cost and the EPC problem is still not solved", 

I've kept track of all the faults on my VW Polo, and it fills a foolscap page.  It ranges  from interior parts falling off, the foot rest lodging itself under the brake pedal whilst driving, the brakes randomly engaging and causing under steer, to continual  creaks from the suspension, the gearbox is crap, not to mention my daily battle with an EPC issue. My Polo's been back to VW a full 58 days during this  year, yet they still haven't fixed all the issues and  as a result I very nearly caused 2 accidents due to  the on-going braking issue, and the EPC going  into limp mode on an on-ramp,  

I've spent more than a  year trying to solve  the problem “EPC” light problem, I've already  replaced  the Acceleration pedal, Two sensors located  under the engine, Cambelt kit, Throttle Body, all the  injectors and the ignition coils and the ECU,   but the light still regularly comes on,  

The VW guaranteed future Value a Rip-Off! I have never  been so dissatisfied with help from customer service and  will NEVER EVER purchase another Volkswagen nor recommend it to anyone I know, because of the shoddy  way we were treated. The staff working in VW credit and financial are rude and disorganized, no wonder they losing all their customers.They charged me for items covered by the warranty.

And the list goes on. These are only a few of the nice clients  I wouldn't want to repeat what some of the other "not so nice" clients said about Volkswagen and their cars, especially about the EPC light and limp mode. Electronic power Control (EPC) has become part of every VW, Audi, Skoda and Seat owners vocabulary, yet few understand what it really is. So allow me to put you in the picture.

Electronic Power Control

The EPC warning light is just a regular warning indicator light, much like your handbrake light or your oil indicator light.  The handbrake light just tells you that the hand break is engaged, alternatively that it hasn't been released. Likewise the oil light is a warning indicator that alerts the driver to the fact that the oil is low. In the very same vain the EPC warning  light is just an indication that something awry has happened in your Volkswagen's torque system, which is a sub-circuit of the Electronic Power Control Circuit.  

So what exactly is the torque system ? you may ask. Well is consists of various interlinked components, where the functionality of one is subject to another. These components are your  Volkswagen's entire drive-by-wire system, incorporating the  accelerator pedal, the throttle body, the cruise control, the traction control, the breaking system, the fuel pressure system, the knock sensors and the ECU, along with the wiring harnesses that inter-connects all these components. The wiring harness is a safer substitute for accellerator cable in all drive-by-wire systems.  

The accelerator pedal

The accelerator pedal for that matter, has 2 independent potentiometers inside a module that's permanently bonded to the pedal itself. These 2 potentiometers are call senders by Volkswagen and known as G79 and G185, but I will use these terms interchangeably.  This module is connected to the ECU via a 6 wire harness, essentially 3 wires per senders. Before, I continue, let me tell you what a potentiometer is, if you not familiar with the term. Another name for a potentiometer is variable resistor or a rheostat. It is most commonly used as rotary the control knob on a radio, with which to control the level of its volume. It is also commonly used in  the bedroom light dimmer to adjust the level of light needed. 

Each sender has 3 pins, 1 for each end of its resistor and 1 pin for its wiper. All three pins of each sender are connected to 3 pins specific pins of the ECU. The ECU sends each sender a high and a low voltage across their resistors and receives a difference fed back voltage from each sender's wiper. The 2 wiper feedback voltages are referenced and inverted to one another and translated by the ECU as how much the accelerator pedal is depressed.  Should  the ECU loose either of the wiper inputs for even a fraction of a second, the ECU limp mode program will execute, the EPC light will come on and the engine wont rev higher that 2000 rpm any longer. When my EPC light came on, I traced it back to a fault/ intermittent accelerator pedal due to error codes P1630  to P1634 and P1639.

The throttle body

Much like the accelerator module, the throttle body also has 2 integrated potentiometers called angle sensors known as G186 and G187. They inform the ECU how wide open or closed its butterfly is. The throttle body also has a built-in stepper motor known as an actuator. The ECU essentially translates the accelerator pedal position to a voltage / pulse train that drives the stepper motor, that in turn opens and closes the throttle body butterfly, controlling  air flow between air filter and intake manifold.  In a nutshell, a remote control system that mimics the operation of an accelerator cable. If for any reason the throttle body is removed or dismantled, it would be necessary to perform the adaptation procedure. When my EPC light came on, I traced it back to a  throttle body problem with error codes P1171 - Angle Sensor 2 for Throttle Actuator (G188) Implausible Signal.

The cruise control

When the cruise control is enabled, a signal is sent to the ECU to this effect, which in turn sends the necessary voltage / pulse train to the throttle body stepper motor to keep it steady and received feedback from G186 and G187 to further control the process., ignoring the accelerator pedal until the brake is applied or receiving a signal change from the accelerator pedal. Should something go awry in this process, cruise control will be canceled, the ECU limp mode program will execute, the EPC light will come on and the engine wont rev higher that 2000 rpm any longer. When my EPC light came on, I traced it back to a  cruise control switch problem with error codes  00895 - Cruise Control Switch (E45) Defective.