Automotive Electronics

Automotive electronics represent a significant chapter in the success story of the 20th century's electronics industry. This field has given birth to a plethora of innovations, from electronic components and printed circuit board design to the internet, computers, fiber networks, communication protocols, wireless transmission, and cell phones, among others. The impact of electronics spans across various sectors, including automotive, aerospace, and medical industries.

In the automotive sector, electronics have ushered in a new era of innovation, revolutionizing the modern-day automobile. From basic radio systems to autonomous vehicles capable of operating without human intervention, the integration of advanced electronic technologies has reshaped the automotive landscape. However, many of these advancements have been spurred by government mandates, such as On-Board Diagnostics (OBD).

On-Board Diagnostics has played a crucial role in the automotive industry's response to global warming, greenhouse gas emissions, and climate change. Mandated by legislation and driven by international initiatives like the United Nations Framework Convention on Climate Change (UNFCCC), OBD systems are designed to monitor and control vehicle emissions, contributing to environmental sustainability efforts.

The evolution of OBD from its inception to the current OBD-II standard has been instrumental in regulating vehicle emissions and promoting fuel efficiency. With the implementation of microprocessor-driven Engine Control Units (ECUs), manufacturers can optimize engine performance and reduce exhaust emissions effectively. However, this shift has also posed challenges for auto repair shops, necessitating the development of third-party diagnostic software compatible with OBD-II systems.

Tools like VCDS, OBD Auto Doctor, and Advanced Driver Assistance System (ADAS) have become essential for mechanics to communicate with ECUs and diagnose engine issues effectively. Additionally, the standardization of protocols like ISO14230-4 (KWP2000) and ISO 15765 CAN network has facilitated seamless communication between vehicles and diagnostic equipment.

The integration of catalytic converters, O2 sensors, and various other components into modern vehicles has become standard practice, contributing to cleaner and more efficient engines. However, this comes with an additional manufacturing cost, ultimately borne by consumers. Furthermore, it has necessitated continuous learning and adaptation among mechanics to keep pace with the rapid advancements in automotive electronics, mirroring the challenges faced in the medical industry with the advent of electronic medical equipment.

In essence, automotive electronics have reshaped the way vehicles are designed, manufactured, and maintained, ushering in an era of innovation and environmental responsibility. As technology continues to evolve, so too will the role of electronics in shaping the future of transportation.

 

Unlocking the Mysteries of Automotive Diagnostics

Unlocking the Mysteries of Automotive Diagnostics

In the intricate world of modern automotive technology, the ability to diagnose and troubleshoot issues has become an indispensable skill for both mechanics and car enthusiasts. One of the key frameworks governing this diagnostic landscape is the Onboard Diagnostics (OBD) system, specifically the second iteration, OBD-II, which adheres to the standards set by the Society of Automotive Engineers (SAE).

SAE and OBD-II Standards:

The SAE plays a crucial role in establishing standards that govern automotive diagnostics. In the context of the VW Polo and many other vehicles, OBD-II is the standardized system designed to monitor and report the performance of various vehicle systems, ensuring compliance with emission regulations.

Stoichiometry and Emission Control:

Understanding stoichiometry is fundamental to comprehending OBD-II's role in emission control. Stoichiometry refers to the chemically balanced ratio of air to fuel necessary for complete combustion. OBD-II monitors this ratio through sensors, with the Oxygen Sensor System (OXS) playing a pivotal role in providing feedback to the engine control module (ECM).

EPC Light - Electronic Power Control:

One of the telltale indicators of an issue within the electronic realm of the VW Polo is the Electronic Power Control (EPC) light. This warning light illuminates when the system detects a fault affecting the engine's performance. The EPC system is responsible for managing the throttle, ensuring optimal power delivery and efficiency.

Check Engine Light and DTC Codes:

The infamous Check Engine Light (CEL) is another beacon of concern for drivers. When illuminated, it signals potential issues with the engine or emissions system. Diagnostic Trouble Codes (DTC), communicated through the OBD-II system, provide mechanics with specific information about the nature of the problem, allowing for a targeted and efficient diagnosis.

Limp Mode and Safety Features:

In the event of a critical issue, the VW Polo employs a safety feature known as Limp Mode. This mode restricts the vehicle's performance to prevent further damage, allowing the driver to reach a service center safely. Understanding the triggers for Limp Mode requires decoding the specific DTCs stored in the OBD-II system.

Sensors, Senders, and Actuators:

Central to the OBD-II system are an array of sensors and senders strategically placed throughout the vehicle. These components, such as the Oxygen Sensor, monitor various parameters and relay information to the ECM. Actuators, controlled by the ECM, respond to these inputs by adjusting engine functions to maintain optimal performance and emissions.

16-Pin OBD-II Connector:

Mechanics rely on the 16-pin OBD-II connector to interface with the vehicle's diagnostic system. This standardized connector provides access to the wealth of information stored within the OBD-II system, facilitating precise diagnosis and troubleshooting.

Automotive Acronyms:

Navigating the world of automotive diagnostics often involves deciphering a myriad of acronyms. From EPC to DTC,to HVAC, to OXS, to EGR and beyond, mechanics adeptly use these shorthand terms to  efficiently communicate and clients and pinpoint issues with precision.However, it can confuse the hell out of them.

Delving into the realm of automotive diagnostics for the VW Polo unveils a sophisticated interplay of technologies governed by SAE standards and OBD-II protocols. Mastery of these systems empowers mechanics to unravel complexities, ensuring optimal performance and emission control for vehicles on the road. 

As technology continues to advance, a deep understanding of automotive acronyms and diagnostic intricacies remains paramount for those entrusted with keeping our vehicles running smoothly. However, it would be feasible even advisable for vehicle owners to get get up to speed with Automotive technology. Technology is here to stay and no matter how hard we try, cannot will it away.

VW POLO CANBUS

If you own a Volkswagen Polo, you more likely that not already know that a Controller Area Network (CAN) bus is an automotive wire network loosely referred to as a bus. The word "bus" comes from the electrical power distribution sector where bus-bars were considered a metalic strip made of copper, brass or even aluminium that served as a source of electric power to the load. 

CAN BUS

However CAN Bus is more akin to Ethernet than a bus-bar. Ethernet is a computer networking technology using Unshielded Twisted Pair cable (UTP) either CAT5 or CAT6 which is now commonly used in local area networks capable of sending  IPv4 / IPV6 packet across its networks at speeds ranging from as slow as 10Mb/s to as fast as 1000 Gb/s, hardware dependent of course. 

Twister pair electrical wires with various colour tracers.

Likewise CAN is a network technology commonly used in automotive networks capable of sending CAN-frames across its network at various speeds, again application dependent. It is essentially a  very reliable multi-master arbitration free serial bus, connecting numerous Electronic Control Units (ECUs) aka nodes together.

CAN BUS vs ETHERNET

The big difference between the two, is that Ethernet is an 8-wire bus comprising of 4 unshielded twisted pairs of wire, each with a specific colour coding, whereas CAN has only a single unshielded twisted pair of wires also with a specific colour coding. The CAT5 protocol insists on 2 twists per centimeter and CAT6 with more twists per centimeter whereas the CAN protocol insists on a 1 turn per centimeter. The lay of these wires are very specific and necessary to reduce or cancel interfering signals picked up from the environment by them, which is more commonly referred to as "crosstalk".

CAN BUS HIGH & LOW

Bearing in mind CAN comes in two varieties used for different functions, viz CAN-High (CAN-H) and CAN-Low (CAN-L).  CAN-H is used for the Powertrain, the Convenience and Infotainment buses. 

Whereas CAN-L is used for the rest of the bus wiring.  Both CAN-High and CAN-Low uses different colour wires for different makes of vehicle. For example:-

Manufacturer        CAN High        CAN Low

Mercedes                  Brown/red         Brown

Volvo                        White                Green

Vauxhall                   Green                White 

BMW 1 & 3             Green/orange     Green 

BMW 5 & 6             Black                 Yellow 

Porsche                     Yellow              Black

The big difference between the three buses for VW,SEAT, Skoda and Audi is that:-

1) The Powertrain bus wires interconnected to all the powertrain modules / nodes are coded Orange & Black CAN-H 

2) The Convenience bus wires interconnected to all the convenience modules / nodes are coded Orange & Green CAN-H 

3) The Infotainment bus wires  interconnected  to the infotainment modules / nodes are coded Orange & Violet /Purple CAN-H 

4) CAN-L bus wires to all the interconnected convenience modules / nodes are coded Orange & Brown. (Electronics colour code 31)

REPAIRING WIRES

CAN wires are typically multi-strand 0.35mm to 0.5mm square with 120 ohm termination impedance, capable of transmitting information using two complementary signals which makes them even less prone to crosstalk. But thin wires are prone to break and if and when they do, it is recommended  that when repairing these CAN Bus wires, that both wires must always remain the same length and of equal thickness. 

Implying CAN BUS is extremely unforgiving. So, when wire 1 of the pair is broken, wire 2 should also be cut and the piece of wire added in-between must be exactly the same length; and that the lay length of 1 turn per centimeter must be observed. 

ELECTRICAL INTERFERENCE

Failure to do so, may created a discrepancy in the wire length of the one wire in the twisted pair as well as in their differential voltages, hence result in network errors — ground noise, electrical interference, hum, buzz,  spark plug spikes — cannot and will not be appropriately cancelled. 

Whenever repairs are made to any CAN Bus wiring, it is highly recommended that all CAN Bus wire repairs are covered and highlighted with yellow insulation tape to signify to anyone doing successive work, that a previous repair was carried out. 

That EPC light.

The most likely reason you're reading this blog post, is because you encountered an EPC fault with your Volkswagen vehicle. I bet you wondered what that yellow/orange light was when it lit-up or perhaps startled when you car went into "limp mode". Whether you're driving a VW Polo or VW Jetta, VW Golf,  VW Caddy, VW Passat, T-Cross, Sharan, Touareg, Transporter, or any other Volkswagen or even a German Audi, or a Czech Skoda or a Spanish VW SEAT, you've come to the right place because they all have an  Electronic Power Control circuit. 

In fact all "modern day" vehicles have EPC circuit, which loudly says that the automotive industry have finally reached some consensus on standardization. But let me tell you what the EPC light actually is. It's just a signal light informing you that there is an error in your vehicles torque circuit. That's the short answer, however, I can tell by the look on your face that it wasn't a  satisfactory answer, so let me give you the long version.

The EPC light is part of the Electronic Power Control Circuit which is just one of the components of OBD-II which was mandated by a certain regulatory bodies with regulatory intent. Their initial intention was to limit carbon emissions / exhaust fumes from cars on the street of America. 

The California Air Resources Board (CARB) and the Environmental Protection Agency (EPA) together with the Society of Automotive Engineers (SAE) and the International Organization for Standardization (ISO) collectively originated the On-Board Diagnostic (OBD) System because of high levels of smog produced by automobiles throughout the USA.  

Their initial On-Board Diagnostic System was subsequently superseded by the all new and improved verion OBD-II, hence all cars manufactured post 1996 has an Electronic Power Control Circuit and by extension an EPC light. The European on-board diagnostics (EOBD) regulations are the European equivalent of the American OBD-II. 

On-Board Diagnostic (OBD-II) is an automotive mechatronic, micro processor / micro controller based computer system with programmed presets that continuously monitors inputs from numerous sensors fitted through the car. 

It then computes/compares/ compensates these inputs against stored data and drives various actuators to perform certain tasks. In a nutshell OBD-II is an input/output (I/O) information processing system much like the PC / laptop / or even your smart phone. By example, a keyboard, a mouse, a joystick, a scanner and a microphone are common computer input devices whereas a HD monitor, a printer, speakers and headphones are common computer output devices. 

Here the computer/laptop makes calculations based on its internal operating system and software to do something intelligible for humans. However in the case of OBD-II, its CPU (Central Processing Unit) is called an ECU (Electronic Control Unit) and among its input sensors are the Accelerator Position Sensor, Mass Air Flow sensor (MAF), Lambda O2 Sensor, Knock sensor, Oli level sensor, Coolant Temperature Sensor, the Camshaft Position Sensor, the Crank Position Sensor, the Wheel Speed  Sensor etc, to mention but a few.

Among its output actuators and solenoids are the drive-by-wire electronic throttle actuator, the fuel injectors, the EPC light, Malfunction Indicator Light (MIL), the Immobilizer, the Airbags and the Power Steering Pump, etc, again to mention but a few,

This ECU is sometimes referred to as an Engine Control Unit especially when intending to make reference to the TCU (Transmission Control Unit). The ECU is sometimes even called ECM (Engine Control Module) when making reference to other electronic control modules like the ABS module, the Instruments module, the Central Electronics Module, the CAN gateway module, the Radio Module, etc, again to mention but a few 

However, the ECU and the TCU are collectively referred to as Powertrain Control Module (PCM). The ECM essentially controls the efficiency of the engine performance by using a Crankshaft Position Sensor to determine the position of the cams in order to activate the injection of fuel into the cylinders and the timing of the ignition spark to ignite it at precisely the correct moment in petrol engines. 

Likewise the ECM in Diesel engines, plays a huge role in the success of the turbodiesel models. But in order for this to happen, an electronic throttle control had to be introduced, replacing the  cable from the pedal to the carburetor system which was prone to idle speed deviation between a hot and cold engine that became more and more prevalent as the components wore out. 

In so doing, the ECM can adjust the electronic throttle angle during acceleration to achieve the right quantitative relationship ratio between the actual airflow through the engine and the injected fuel thus maintaining Stoichiometry. Controlling the throttle airflow on the fly, markedly improves overall torque and driveability which is known as torque-mapping, an advantage that is only possible with drive-by-wire. 

So, the Electronic Power Control Circuit consists of the ECM, the Accelerator Position Sensor, the Throttle Position Sensors, the Throttle Actuator, the MAF / Air Filter, the Fuel Injectors, the High Pressure Fuel Pump, Fuel Temperature Sensor, Fuel Rail Pressure Sensor and Pressure Relief Valve. 

The single accelerator position sensor is made up of two individual potentiometers each acting independently of the other but collectively operate with opposite polarity voltages supplied by the ECM, as a safety back-up for one another. 

Thus, if either potentiometer fails, the ECM will activate limp mode. This is a safety measure that prevents the system from acting as if it had an accelerator cable that got stuck in the runaway position and the makings of a potential accident. The cruise control also has influence on the throttle body and requires the brake pedal to be depressed to cancel the cruise control. 

The ECU normally takes this cancellation signal from the brake light MOSFET low-side driver in the ECU. So either the brake pedal switch and the a brake light bulb can cause an EPC error along with the aforementioned fuel supply components. It's best to have a diagnostic tester to check for DTC errors via the DLC connector. It would at the very least steer you in the right direction to fix your EPC problem effectively.

Electronic Power Control (EPC)

It was very surprising to discover how many thousands if not millions of car owners out there, have no idea exactly what  Electronic Power Control (EPC) is. Yet most of them would like to know what the Electronic Power Control (EPC) circuit really does , more especially the Volkswagen, Audi, Seat and Soda owners. 

Considering they've been plagued by the Electronic Power Control (EPC) light, limp mode, DTC errors and poor engine performance to the point of frustration and panic for a number of years. Nobody seems to be able to give them good advice or practical guidance; and in many cases not even the Volkswagen, Audi, Seat and Skoda agents can. 

Leaving VW owners confounded, disappointed and disillusioned by their choice in cars, which results in so many car owners swearing, never to invest in VW brands ever again.

Unscrupulous motor mechanics tend to take advantage of these situations, recommending that the car owner brings their car to them as soon as possible before damage occurs to the engine.  Whereas in fact, the Electronic Power Control (EPC) is a safety circuit designed to prevent damage to the engine. 

When the  Electronic Power Control (EPC) mode does engage, it can and often does affect the car's stability and cruise control and torque circuit giving the impression there is a lot more wrong than there actually is. 

Since the Electronic Power Control (EPC) is "yellow" and not red, it acts more as an advisory light rather than a warning light, even though everybody tends to call it a warning light. A  flashing amber light is considered a "warning signal" but still doesn't have the danger status of "red warning light". 

 


Technically the "yellow" Electronic Power Control (EPC) light is in fact  amber which is a blend between orange and yellow. Car dashboard light colours can be roughly divided into three categories. 

Warning lights are Red in colour. Advisory lights are  amber in colour and information lights are generally either white, green or blue in colour. Having said that, its simple to understand that amber implies that you should keep an eye on, or be prepared for either  a reduction in power or  interruption to power.

Hence, Amber lights are used as Indicator lights (flashers) on cars for the turn signal and hazards. Amber lights are also used by roadside breakdown vehicles to alert drivers. An amber traffic light is generally considered a cautionary light, signalling  readiness to stop. Much like an amber  traffic light does. 

Now that you know what the colours of the lights imply, allow me to give you the low-down on Electronic Power Control (EPC) itself. EPC is an acronym and it is the official abbreviation for Electronic Power Control. 

Electronic Power Control is an embeded system, specifically designed into electronic circuits that permits it be part of a larger electro-mechanical system.  An Electronic Power Control system can also simply be described as a self-contained "feedback" circuit.  

It can even be further  explained, as a microprocessor based electronic circuit -or a computer if you like- that alters its output bias based on its inputs. Its "status quo" or current baseline is taken as a reference point and the objective is to control its operation within its predetermined parameters, and as close as possible to the said baseline, based on the signals from its inputs. 

Should any of these inputs, that predominantly come from sensors fail, for whatsoever reason, the computer circuit wouldn't be unable to complete its processes and would either enter into a "compensatory state", a "warning state" or an "error state". But more about this later!

The Electronic Power Control circuit has become standard equipment as part of the OBD-II (On-board Diagnostics 2) system in all modern day cars, manufactured since 1996. The Electronic Power Control is an integral part of every computerized ignition and engine management system, embedded into the ECU (elcectronic computer unit). 

The Electronic Power Control (EPC) dashboard advisory light is also part of this system and is normally activated by errors in the vehicle's torque circuit but not exclusively. The Electronic Power Control (EPC) light is  actually  a "new" addition to the plethora of light on the more modern vehicle's dashboards, a light  that gives any driver a sense of despair when it turns on. 

But more about that later ...

However, since a full blown explanation is outside the scope of a single blog-post, it is imperative that you need to read  every blog installment or the entire blog to get the full Electronic Power Control (EPC) picture.

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The Most Common Car Problems

There was a time when car owners could easily service their own cars. Simply replacing points, plugs and condensors,  draining its oil and replacing its oil and oil filter normally put the car back on the road again. Those were the days when the most common roadside problem was a puncture or a snapped fan belt. Punctures were easily fixed with a replacement tyre from the trunk. All that was needed was some elbow grease applied to the jack, wheel brace and wheel nuts and you were on the road again. But today rollbacks are are integral part of motoring. Hundreds of cars are loaded up everyday on the road side.

The main cause of punctures was attributed to poor road surfaces, random metal objects and broken glass and to a lesser degree older tyre technology. Even though punctures were predominant, they were by no means exclusive to roadside breakdown because clutch plates and gearbox problems were also plentiful, as was running out of fuel.

With the advent of newer cars, the race for the most fuel efficient and least expensive car was on. When fuel and air stoichiometrics were at its peak, car manufactures started producing cars with a 'Space Saver Biscuit Spare Wheel' which took several kilograms of weight out of the trunk, This made the car a tad lighter, slightly more fuel efficient and ever so slightly, cheaper to produce.

Today, almost a third of all new cars don't even have a spare wheel; instead they may be equipped with a can of self inflating puncture-repairing foam, or an electrical air compressor with some sealant kit to temporarily fix a flat tyre. Both options are evidently cheaper than a Space Saver Biscuit Spare Wheel and lighter.

However, believe-it-or-not, the more expensive cars today, are sold without  a spare wheel, instead they are fitted with “run-flats”. In a nut-shell, run flats are special pneumatic tyres, designed to resist the effects of deflation when punctured, yet enables the car to  be driven at reduced speeds of under 90 km/h for a distance of up to 80 km. The speed and distance of course to the nearest tyre repair shop, is subject to the type and quality of the “run-flats”.  So, once again the manufacturer saves the cost of supplying a spare wheel.

Be that as it may, snapped fan belts  often causing the engine to overheat, sometimes resulted in a  blown  cylinder head gasket. Subsequently, the modern day electric radiator fan has totally supperceeded the belt driven fan and as a result, burst radiator hoses, corroded, leaking water pumps and welch plugs have  became the primary cause  of blown cylinder head gaskets. The other bugbear is oil leaks that weren't timeously attended to, currently trending as the most common cause of seized engines. 

With the abundance of electronics fitted into cars, the alternator  and its voltage regulator have  became a lot more more troublesome than ever before. Obviously due to the additional electrical load.  Alternator  problems are closely followed by starter issues when either its brushes or its  bendix reaches its end of life.   

Both types of problems have resulted in batteries being replaced prematurely and sometimes unnecessarily. Brakes and Turbos also give their fair share of problems, but none of these problems comes close to the new type of roadside breakdowns caused by the OBD-II system.

The most common cause of  breakdowns today, is the Electronic Power Control (EPC) light; not that the light is the cause of the problem. The Electronic Power Control (EPC) light is only an advisory light, drawing your attention to a possible malfunction or  pending problem or  already existing problems.

When the Electronic Power Control (EPC) light comes on, without the ESP or Check  engine light, the car is normally still driveable, even if it goes into limp mode. But when accompanied by the ESP and or CEL (check engine light) the car may refuse to start as its inhibited by the Electronic Computer Unit (ECU). 

When this happens, the only solution is to secure a rollback to fetch the car and take it either to your service agent / mechanic or your home, so that you can tend to the problem yourself. 

There is no way you'd be able to effect repairs to your car yourself without a OBD II scanner   that would direct you to, or confine your repair to a certain area of the engine. 

Below are a few sample yet partial ODB II diagnostic scans  for Electronic Power Control (EPC) problems. 

This for a 7N0 - VW Passat.
Address 01: Engine (CDL)       Labels: 06F-907-115-CDL.clb
   Part No SW: 1P0 907 115 AB    HW: 8P0 907 115 B
   Component: 2.0l R4/4V TFSI     0020  
   Revision: 5BH20---    Serial number: 0000              
   Coding: 0303004C18070160

1 Fault Found:
008487 - Accelerator Position Sensor 2 (G185) 

               P2127 - 002 - Signal too Low

Electronic Power Control (EPC) problem  for a 1J - VW Golf.

Address 01: Engine Labels: 06A-906-032-AWP.lbl

Part No: 06A 906 032 RN

Component: 1.8L R4/5VT G 0001 

Coding: 07510

18047 - Accelerator Position Sensor 1/2 (G79/G185) 
            P1639 - 35-00 - Implausible Signal
18042 - Accelerator Position Sensor 2 (G185) 

            P1634 - 35-10 - Signal too High - Intermittent

Electronic Power Control (EPC) problem  for a 7L - VW Touareg 

Address 02: Auto Trans        Labels: 09D-927-750.lbl
   Part No: 09D 927 750 AN
   Component: AL 750 6A           0546  
   Coding: 0004153


1 Fault Found:
00777 - Accelerator Position Sensor (G79) 

            004 - No Signal/Communication - MIL ON

NB! The Automatic Transmission module and not the Engine Module detected this accelerator sensor problem.

 

Electronic Power Control (EPC) problem 1H - VW Golf/Vento III
Address 02: Auto Trans       Labels: 01M-927-733.LBL
   Controller: 01M 927 733 CT
   Component: AG4 Getriebe 01M    3363
   Coding: 00000
    

1 Fault Found:
00518 - Throttle Position Sensor (G69)

            16-10 - Signal Outside Specifications - Intermittent

NB! The Automatic Transmission module and not the Engine Module detected this accelerator sensor problem. Here the Throttle position sensor instead of the Accelerator sender is the cause of the problem.

Electronic Power Control (EPC) problem  for a 9M - VW Jetta IV.
Address 01: Engine Labels: 06A-906-032-AWP.lbl
Part No: 06A 906 032 RN
Component: 1.8L R4/5VT G 0001 
Coding: 07510

1 Fault Found:
18047 - Accelerator Position Sensor 1/2 (G79/G185) 

P1639 - 35-00 - Implausible Signal 

Electronic Power Control (EPC) problem  for a 8E - Audi A4.
Address 01: Engine Labels: 06C-909-559-ASN.lbl
Part No SW: 8E0 909 559 D HW: 8E0 909 059 
Component: JHM V3/9X G 0003 
Coding: 0016751

2 Faults Found:
18047 - Accelerator Position Sensor 1/2 (G79/G185) 
P1639 - 008 - Implausible Signal - Intermittent
18047 - Accelerator Position Sensor 1/2 (G79/G185) 

P1639 - 008 - Implausible Signal - Intermittent - MIL ON

Electronic Power Control (EPC)  for a 8P - Audi A3.
Address 01: Engine Labels: 06A-906-033-BGU.lbl
Part No: 06A 906 033 DS
Component: SIMOS71 1.6l 2V 5559 
Revision: --H03--- Serial number: AUX00000
Coding: 0000071

4 Faults Found:
18047 - Accelerator Position Sensor 1/2 (G79/G185)

P1639 - 008 - Implausible Signal - Intermittent

Electronic Power Control (EPC) problem  for a 9M - VW Jetta IV

Address 01: Engine Labels: 06A-906-032-AWP.lbl

Part No: 06A 906 032 LP

Component: 1.8L R4/5VT G 0005 

Coding: 07500

18042 - Accelerator Position Sensor 2 (G185) 
P1634 - 35-00 - Signal too High
18039 - Accelerator Position Sensor (G79) 

P1631 - 35-00 - Signal too High

 Electronic Power Control (EPC) problem  for a 1C - VW New Beetle

Address 02: Auto Trans Labels: 01M-927-733.lbl
Part No: 01M 927 733 EN
Component: AG4 Getriebe 01M 4108
Coding: 00000

1 Fault Found:
00518 - Throttle Position Sensor (G69)

16-10 - Signal Outside Specifications - Intermittent

NB! Once again the Automatic Transmission module  detected this Throttle position sensor instead of the Engine Module detecting the Accelerator sender to be the cause of the problem.

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As can be seen from the data above,  there are essentially 3 types of  DTC errors responsible for triggering the EPC light, though not exclusively. P codes  P1630 and P2122;  P1631 and P2123;  P1632 and P1861 are essentially the same and applies to sender 1. 

As can be seen below.
P1633 and  P2127;  P1634 and P2128; P1639 and P2138 are essentially the same but applies to sender 2. There are also several other DTC errors that can and trigger the EPC and or along with the ESP, and or with the CEL.

Accelerator Pedal Sensor 1

P1630 - Accelerator Pedal Pos. Sensor 1 (G79), Signal too Low

P1631 - Accelerator Pedal Pos. Sensor 1 (G79), Signal too High

P1632 - Accelerator Pedal Pos. Sensor 1 (G79), Power Supply Malfunction

P2122 - Accelerator Pos. Sensor 1 (G79), Signal too Low

P2123 - Accelerator Pos. Sensor 1 (G79), Signal too High

P1861 - Accelerator Pos. Sensor 1 (G79), Error Message from ECM

Accelerator Pedal Sensor  2

P1633 - Accelerator Pedal Pos. Sensor 2 (G185), Signal too Low

P1634 - Accelerator Pedal Pos. Sensor 2 (G185), Signal too High

P1639 - Accelerator Pedal Pos. Sensor 1/2 (G79) / (G185), Implausible Signal

P2127 - Accelerator Pos. Sensor 2 (G185), Signal too Low

P2128 - Accelerator Pos. Sensor 2 (G185), Signal too High

P2138 - Accelerator Pos. Sensor 1/2 (G79) + (G185), Implausible Signal

Throttle Position Sensor

16505/P0121/000289 - TPS (G69): Implausible Signal
16506/P0122/000290 - TPS (G69): Signal too Low
16507/P0123/000291 - TPS (G69): Signal too High

Throttle Angle Sender 1

17950/P1542/005442 = Angle Sensor 1 for Throttle Actuator (G187): Implausible Signal
17951/P1543/005443 = Angle Sensor 1 for Throttle Actuator (G187): Signal too Small
17952/P1544/005444 = Angle Sensor 1 for Throttle Actuator (G187): Signal too High  

Throttle Angle Sender 2

16605/P0221/000545 - Angle Sensor 2 for Throttle (G188): Signal   Implausible 
16606/P0222/000546 - Angle Sensor 2 for Throttle (G188): Signal Too Low
16607/P0223/000547 - Angle Sensor 2 for Throttle (G188): Signal Too High

Depending on the model of your vehicle, its Throttle position sensor (TPS) lowest output voltage should be around .17 Volt and when the Electronic Control Unit (ECU) detects that it has dropped below that, then it will trigger either a P0122 or P0222 code.  High signals are not common but they do occur. 

 

As can be seen from the above data the error signal is either too low or to high or intermittent/implausable. Bearing in mind that a constant 5 volts is supplied by the ECU via a High-side or Low-side driver to the each of these potentiometers (senders). Loss of the voltage or even intermittently loss will trigger the EPC light and enter into "limp mode".

By implication  the monitored output is in 1 of 3 states, viz, low, high, or intermittent. In order to determine these states, the ECU needs a reference to compare these signals against. Each sender therefore act as a reference for another and any discrepancy between the two can result in an EPC error and subsequent limp mode. 

Replacing the Accelerator Pedal sensor (potentiometer)  unit normally fixes the EPC problem, but limp mode can also be caused by the throttle butterfly potentiometer.  And like I mentioned before, an OBD-II diagnostic tester would make this repair a lot easier and a lot faster.


NB! When your car goes into "limp mode", you may have  a lit   "Engine Management Light" (EPC icon) and or a "Electronic Stability Light" (skidding car icon) and or a "Engine Control Lamp" (engine icon) or any other combination thereof.  

Even Earthworks machinery are fitted with OBD-II so that exhaust emissions can be controlled but when there is a problem in the OBD-II system, invariable these machines would have to go on a roll back and taken for repair.

 

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What your Electronic Power Control (EPC) Warning Light really means

Computers are ubiquitous or rather microcomputers, microprocessors and their peripheral systems and chipsets are.  As such, they can be found in most electronic devices, ranging from laptops to printers, routers, radios, walkie-talkies, cell-phones and toys to mention but a few. In fact, microprocessors are so common place that they've taken over most hand held and personal electronic devices so-much-so that they are even embedded in our entertainment equipment, our cars, motorcycles, aeroplanes, ships and trains. It can thus be said that electronics in all its technological forms, have completely changed how we live  our lives. These systems along with its sensors, sendors and actuators are referred to as On-Board Diagnostics (OBD) and since it's in its second revision, known as OBD-II or just OBDII.

Furthermore  these On-board diagnostic (OBDII) digital computers interfaced with its dependency modules, electro-mechanical systems and sensors built into our cars have collectively taken-over and superseded most mechanical linkage functions, that were previously and traditionally used for acceleration, steering control and parking brake among several other.  So, welcome to the world of  drive-by-wire, (electronic throttle control) steer-by-wire, shift-by-wire, brake-by-wire and fly-by-wire which is currently widely used in aviation. 

What your Electronic Power Control (EPC) Warning Light really says!

Your car's EPC light essentially indicates that there is an issue with the  torque system of your vehicle. This torque system is your car's acceleration and braking system that now operates via drive-by-wire, shift-by-wire and brake-by-wire. In a nutshell, it's a computer chip supervised electronic system (ECU) that replaced the cable linkage previously situated between the carburetor and the accelerator pedal with an electrical/electronic interface. 

This amber EPC light is an advisory light rather than a warning light -since warning lights are red in colour- is illuminated when the ECU detects a glitch in the torque system. When a glitch is detected, in most cases the ECU will enable 'limp home mode'. Limp mode is a fail-safe software-embedded, security and safety feature that  inhibits the system, activates a  rev limiter, shuts off boost partially or completely, resulting in a maximum 2500 RPM.  

Thereby leaving only sufficient power to safely drive the car home in some cases. In other cases it could prevent the car from even starting.  Limp mode also acts as a safe-guard against further engine / transmission trouble or possible runaway.  Switching off the engine and disconnecting the battery may in some cases momentarily cure limp mode, but then again it may not due to the ECU's  non-volatile memory. However as an  advisory light, it begs for an OBD-II diagnostic scan, so that the Trouble Code (DTC) error may be diagnosed and repaired. This is best done sooner rather than later, as Limp mode sometimes manages to cures itself, yet bound to repeat itself continually until repaired. The ECU has a counter / timer monitoring how many times the same DTC was detected since the last start-up. If just a few times (considered negligible / mistakenly triggered) the counter resets itself and starts to recount from when it happens again.

Having said that, EPC lights and drive-by-wire systems aren't exclusive to "VAG cars" like most mechanics would have you to believe. The EPC light is a mandatory part  of the OBD-II system hence fitted as standard equipment on "all post '96 cars". OBD regulations are written into Government legislation globally so that in time, the Department of Transport (DoT) may require all vehicles to regularly go for mandatory carbon emission tests in order the achieve road roadworthiness. They will access your cars under dash 16 pin obd connector to check its "Readiness Status". Readiness is an 2 x 4 digit binary number (hexadecimal) that look something like 1011 0110 or 1110 0101 or 0000 0000 or any combination of zeros and ones which is subject to the workings of equipment fitted in your vehicle.

Anyway, if you don't know, VAG stands for Volkswagen AG. The AG is an abbreviation for Aktiengesellschaft - implying incorporated. Aktiengesellschaft is the German term for a Public Limited Company (PLC). Thus the  VAG group is comprised of ten car brands  viz, Volkswagen, VW Commercial vehicles, Volkswagen Marine, Audi, SEAT, CUPRA, ŠKODA, Lamborghini, Porsche, Bentley and Ducati, spanning across five European countries.  In a nutshell most if not all these vehicles have a EPC light and torque control circuit operated via drive-by-wire as standard equipment. But as mentioned previously, an EPC lights with drive-by-wire and brake-by-wire is not exclusive to VAG cars.  

This torque circuit (throttle-by-wire) is a collection of interconnected electronic components amongst which are the car's battery, ignition switch, throttle body position sensor / potentiometer and throttle body actuator / stepper motor. The ECU itself, the braking system sensors and the wiring harnesses that supplies voltage / earth and feedback to and from the accelerator position sensor/ potentiometer and the throttle body motor, the cruise control switch, the instrument cluster and even one of the brake globes itself.

Possible problems

So by implication, with so many points of failure, so much can go wrong, For example, a loose battery terminal could cause the accelerator potentiometer input voltage to momentarily disappear for a fraction of a second, thus detected by the ECU which  would then trigger limp mode. It could also be caused by a speck of dust has settled on the potentiometer slider that creates a brief intermittent contact. The ECU will however detect this and implement limp mode. 

Then there is the dozens of wiring harnesses with their hundreds of connections. Several of them instrumental in the automotive torque circuit. Since electronics has taken over our cars, some having more than 3 dozen individual harnesses, collectively  comprising of more than 3000 wires and a third as many connectors. It gives you an idea of multitude of electrical problems that can occur.

Male and female wiring harness connectors used in the automotive industry are fairly reliable however due to the under-bonnet conditions like extreme engine heat and morning freezing temperatures, humidity, steam, condensation, oil splatter, dust and vibration, can collectively give rise to corrosion inside wired plugs and sockets. Corrosion normally causes high resistive electrical conditions which upsets the functionality of the circuit concerned.  

This could cause a myriad of problems in a myriad of circuits among which could be the MAF circuit, causing poor driveability and sudden jerking motions during acceleration flanked by untimed detonations.  It could be the MAP circuit causing poor fuel economy and difficult starting and rough idling. Catalytic converter wiring would cause dark exhaust smoke that  smell like rotten eggs due to the excess sulphur and the engine performance will be sluggish..... etc. Wait for the follow-up!