Annoying VW EPC light

VW EPC expounded

As I've explained in an earlier blog, the amber Electronic Power Control warning light on your car's instrument cluster, is just an indicator light; drawing your attention to either (1)  an Auto-Correct EPC Problem, (2) a Pending EPC Problem, (3) an Existing EPC Problem or  (4) a Current EPC Problem. 

An Auto-Correcting  EPC problem occurs when the EPC light goes on without noticeable difference in engine performance and goes off during subsequent drive cycles which may be within a day or two or longer.

A Pending EPC Problem could be something as simple as a spark plug misfiring intermittently and appears in the scan list but after a while becomes an Auto-Correcting EPC problem alternatively if the plug continues to misfire it becomes and Exising EPC problem.

An Existing EPC Problem could be something like the MAF sensor or a accelerator pedal sensor that needs cleaning or replacement and a Current EPC Problem normally results in limp mode.

EPC light is bright YELLOW/AMBER and acts as a indicator, it is not as a warning light. 
Warning light are always RED.

EPC light is bright YELLOW/AMBER and acts as a indicator light, an advisory light; it is not as a warning light.  Warning light are always RED. Since the ECU "learns your driving style" over time, it records your optimize drive cycles to non-volatile memory along with atmospheric pressure, min & max rpm and the average fuel use data, etc, then creates an adaptive pattern or map based on these parameters. 

When this map is compared to sudden spirited driving, it may trigger the EPC light but will auto-correct (reset) itself after a few driving cycles within a day or two. Sometimes the EPC light may be accompanied by the Check Engine Light (CEL).

A Pending Problem can cause the EPC light to come and not switch off on its own. Pending implies that the problem will only get worse if left unattended to. A diagnostic scanner is needed to view the DTC error, hence its really worthwhile investing in one. 

For example, assume that cylinder number 3 randomly misfired a few times as the pending problem. The scan freeze frame data will show something like this.

000771 - Cylinder 3

               P0303 - 000 - Misfire Detected - Intermittent

             Freeze Frame:

                    Fault Status: 00100000

                    Fault Priority: 2

                    Fault Frequency: 7

                    Reset counter: 255

                    Mileage: 38187 km

                    Time Indication: 0

                    Date: 2021.11.05

                    Time: 21:09:58

             Freeze Frame:

                    RPM: 758 /min

                    Load: 13.1 %

                    Speed: 0.0 km/h

                    Temperature: 51.0°C

                    Temperature: 33.0°C

                    Absolute Pres.: 830.0 mbar

                    Voltage: 12.435 V

What this means is that cylinder misfired 7 time, and that the most recent misfire occurred at the displayed time and date highlighted in red and has a fault priority of 2.  Fault priority of 4 or lower needs to be attended to immediately since it affects the driveability of the car. Don't ignore the VW EPC light.  

Fault priority of 5 and above doesn't require immediate attention but must be attended to sooner rather than later. The freeze frame date shows that the car was idling and 758 rpm with the speed at 0 kph and that the engine hasn't reach its optimum operating temperature as yet. In a nutshell, freeze frame captures the engine operating conditions at the time when the EPC error occurred.

An Existing EPC Problem could  mean either the throttle pedal, throttle body, or brake control unit or any other circuit related to the torque circuit, like the  cruise control unit or the traction control unit is misbehaving.  However the EPC light can also indicated an unrelated problem like a loose fuel cap. With the EPC light on, and a pungent fuel smell inside the cockpit would point you to fuel cap.  

Since the fuel is under pressure, the fuel pump, fuel regulator or fuel rail pressure sensor may also be suspect, each should be excluded through a process of elimination. Remember the Electronic Power Control system is integrated with several other systems on you vehicle, like the steering control unit and the ECU, hence it's not always easy to diagnose.

Its permissible to  drive your VW for a short distances and for a short period of time after the EPC light has triggered, that's to say if driveability hasn't been impaired but its best to either fix it yourself or take it to  VW service center. An  EPC dashboard light can be caused by any of the following, but in no particular order. Sometimes both the EPC light and CEL (check engine light) would turn on.

1) Brake Light Switch failure

2) Mass Air Flow Sensor failure 

3) Engine Speed Sensor failure 

4) Throttle System Potentiometer Failure

5) Cruise Control failure

6) Accelerator Pedal Potentiometer failure

7) Repeated cylinder misfires

8) Loose fuel cap

9) Blown / Faulty  brake light

Any of these can and may cause your vehicle to go into “limp mode” which can be described as a Current EPC Problem. When limp mode strikes, the Engine Control Unit will limits the functions of the torque circuit and transmission thus prevent your VW's engine from  revving higher than 2000 rpm and limit its speed to 30-45 kpm. 

Some mechanics would reset the EPC light by cleasing the DTC list without fixing the actual problem but this is not recommended. When the  Diagnostic trouble codes (DTC) are cleared,  "your driving style" map is also deleted, meaning that the ECU would have to relearn  "your driving style"  from scratch and your VW's performance may seem a bit off.  That's to say, until your racked up sufficient drive cycles (data) with which the ECU can do an analysis in real time. 

Grand Theft Auto

Volkswagen (VW) motor vehicles are not only popular among car enthusiasts, they  are also very popular car among the first-time car-buying youth. That said, VW vehicles have also become most popular car among car thieves to steal.

According the Crime Statistics Report for the years 2020 and 2021 - released by the South African Police Service (SAPS)- motor vehicle theft in general has steadily increased since 2011. However, it is correct thinking to assume that thieves have a preference to certain make and model of car.  Case in point - both the VW Polo hatchback and VW Polo sedan are at a higher risk of being stolen than any other VW model and other manufacture's vehicles as a whole.  

VW Polo Hatchback

Since its release in 2018 the VW Polo Hatchback had become the most stolen cars in South Africa. By 2019 it was the most sold passenger vehicle; targeted by "chop-shops" -illegal garages that buy stolen cars - to disassemble them and sell their individual components for profit - aka midnight spares. 

The new VW Polo hatchback - front-wheel drive, 5 door with 5 seats, powered by a 2.0L TURBO 4 engine that outputs 147 kW of power and 320 Nm of torque costs roughly between R320K and R480K whereas a older model or one with  a lower capacity can sell for anything from R170 000 and R250 000 subject to millage and overall condition.

VW Polo Sedan

The VW Polo sedans comes in as either Trendline, Comfortline, Highline and are essentially the sedan version of the  VW Polo hatchback with and engine capacity of either 63 kW  of 77kW fetching a price between R270k and R350k.

Insurance

Loosing a vehicle of this calibre with such a pricetag can be really gruesome hence a condition of any hire-purchase agreement to keep the vehicle adequately insured but an anti hijack immobilizer and alarm system is also essential. Car insurance coupled to Life Insurance may also be highly advantagious.

Anti-theft Alarm, Remote Central Locking and Remote Central Locking are not standard features of all models but the all do come with an Immobilizer but without Automatic Door Lock. It is therefore feasible to invest in an anti-Blocker, anti-Signal, anti-Jammer engine immobilizer with vehicle tracking GPS tracker support and engine cut in preference of the factory fitted product.

Transponder detection

Since most later vehicles are fitted with receiver and transponders chips, stealing a car without having its corresponding key is quite difficult.  If the key isn't close to the steering column stalk that houses the receiver coil or not within key detection distance then engine will not start.  Thieves also resort to key re-programmers and signal grabbers to counteract new technologies like ‘push to start’ buttons installed in the later model vehicles.

Carjacking

So, in order for thieves to steal your car they would have to take it from you by force  - hijacking, a horrific experience. Most cars today are stolen that way by hijacking the driver. If the thieves don't have the matching ignition key, the immobilizes prevents them from starting it by inhibiting the starting process, hence they take the car from the driver with key by force -carjacking. 

Safety Tips to prevent a possible hijacking

Before getting into your car, look around for any any suspicious characters. Should they be around alert a friend, family member or neighbour, even get them to accompany you.

Hijackings are often than not planned, so be be vigalent and cognizant of vehicles following you even at a distance.

Jot down the number plates of vehicles that or that continually pop up on your daily travels and check against previous ones.

Report any s suspicious activity to your local neighbourhood watch or security company of police.

Make sure that you are not being followed before driving into your driveway where you could be cornered.

Alert someone at home before driving into your driveway, to come outside to observe if there are suspicious characters lurking about.

Always be aware and alert of your surroundings before getting out of your car.

Never stop or park your car in a way that you cannot get away from someone following you quickly. 

Be aware of any vehicle blocking your driveway as you pull into it. Honk your hooter constantly to alert neighbours. It may be sufficient to scare them off.

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.

___________________________________

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!

Common OBD-II Problems

OBD-II has now been in our faces for a "Quarter Century" and even though it works fairly efficiently to control the hydro-carbon emissions in post '96 vehicles to some degree, it isn't as effective as some people would've liked, in terms of its diagnostic accuracy or as transparent and simplistic in its use to aid the layman.  On the flip side, many people with several mechanics among them completely abhors OBD-II and sees it more as a hindrance that a help and even add that they prefer cars not to have OBD-II. Since its inception, OBD-II has stymied mechanics globally, especially when the OBD-II system shuts down the engine and turns on the  EPC Light or Check Engine Light. And today, some 25 years later most car owners and mechanics still suffer fits effects yet endure the wrath of OBD-II. However, regardless of what we as lay people say, OBD-II is here to stay and we cannot wish it or will it away. 

Genuine Volkswagen / Audi Harness Mfg Part #: 1KD971658

Personally I think OBD-II is a great in all aspects and incarnations however it has its drawbacks. OBD-II  does place car owners at a huge disadvantage and at risk when it fails. Purely because the problems are not evident but rather masked by the mysteries of electronics technology. This very often leaves them stranded and in a dangerous situations when stuck in the middle of nowhere. With the result that even the DIY car owners cannot do any repair work themselves, but have to resort to phoning  a salvage company to come  load their vehicle onto  a rollback.  Unless of course they have previously invested in a OBD-II scanner  and is able to check for DTC error codes.  But as the saying goes, "most people only lock the stable after the horse has bolted". 

Another drawback of OBD-II is that since car owners in general do not own diagnostic scanners; so they have to rely on some mechanic workshop or mechanical to tell them what problems they've encountered with their vehicle but only once its repaired. Considering most mechanics / repair shops repair OBD-II errors by substituting parts until the cause of the problem is  solved. Merely because they don't even understand the workings of OBD-II well enough to pinpoint problems with any great success. For most of us, this type of hit-&-miss approach comes as an un-bugeted expense, which most car owners can ill-afford especially after having to pay the exorbitant rollback cost.

I believe there are thousands more vehicle owners today, interested in their own vehicle's maintenance and there are even more inclined towards DIY repairs than ever before because of ODB-II. Their motivating factor being the high cost of automotive repairs vs the low cost of ODB-II diagnostic scanners. Albeit that the lower cost scanners bordering on cheap doesn't do such a fantastic diagnostic scan as their more expensive counter parts. 

NEW GENERATION CARS

Hopefully, the next generation of automobiles will be released with onboard diagnostic scanners incorporated directly into the vehicle's infotainment system. Seeing that these fancy units are comprised of  several discrete devices built into the same platform.  It's quite common for the average touch screen infotainment systems to have features ranging from  Built-in Bluetooth to Built-in WIFI which supports WiFi hot-spot broadcasting. Integrated phone connectivity for calls. Some even have rear view camera support. 

Others have fully fledged full-format 1080P video decoding, and USB functionality with multi-format audio and multi-band radio, coupled to dedicated dual voice-coil subwoofer and surround sound speakers. Not to mention Internet APP download capability.  Some include mirror and link for both Android and IOS Phones and a Global Positioning System (GPS) for navigation. All thanks to the magic of powerful multi-core processors and microprocessor embedded systems. 

I'd say adding an OBD-II scanner in place of one of these gadgets would be more beneficial 

So, throwing in a pretty decent quality OBD-II scanner into such a menagerie of tech wouldn't be such a biggie for car manufacturers and the cost wouldn't be prohibitively expensive either.  But since we not at that point in automotive evolution as yet, most DIY car owners have to rely on the handheld / smartphone diagnostics to scan their cars. 

Be that as it may. Very fortunately there are some common fault lists that would prevent you from having to go buy an expensive OBD-II scanner or go through the agony and trauma of having your car fixed by trial and error. Sharing  common automotive problems for the benefit of other, who are bound to experience the exact same problems in the very near future is a godsend.  Same model cars tend to have the same problems as others but invariable and inevitably those components will fail because obsolescence was part of its initial design. The same components used different model cars tend to fail in the same way and cause the same problems.

We've found that the most common OBD-II problems are associated with misfiring engine cylinders, problematic exhaust Gate Reticulation system (EGR), Oxygen Sensor (O2), Electrical Harnesses and fault Catalytic Converters. Many car owners are decating their diesel models, claiming better performance. But since OBD-II was explicitly introduced to control and reduce carbon emissions, removing it is not such a great idea. 

VW / Audi Harness ES#: ES2993475  

 

COMMON FAULTS 

Erratically idling, or misfiring of bucking or  car goes into limp mode or starts and cuts out all result any one or more of the following error codes:-

P0105 - Manifold Absolute Pressure / Barometric Pressure Voltage supply

P0106 - Manifold Absolute Pressure / Barometric Pressure out of range 

P0107 - Manifold Absolute Pressure / Barometric Pressure Low Input

P0108 - Manifold Absolute Pressure / Barometric Pressure High Input

P0234 - Turbocharger Overboost Condition Control limit exceeded

P0235 - Turbocharger Boost Sensor (A) Control circuit  limit not reached

P0236 - Turbocharger Boost Sensor (A) circuit  out of range

P0237 - Turbocharger Boost Sensor (A) circuit  Low Input

P0238 - Turbocharger Boost Sensor (A) circuit  High Input

P0243 - Turbocharger Wastegate Solenoid (A) Open/Short Circuit to Ground

P0245 - Turbocharger Wastegate Solenoid (A) Low Input/Short to ground

P0246 - Turbocharger Wastegate Solenoid (A) High Input/Short to B+

P1154 - Manifold Switch Over Malfunction

P1155 - Manifold Absolute Pressure Sensor Circuit Short to B+

P1156 - Manifold Absolute Pressure Sensor Circuit Open/Short to Ground

P1157 - Manifold Absolute Pressure Sensor Circuit Power Supply Malfunction

P1158 - Manifold Absolute Pressure Sensor Circuit  out of range

P1400 - EGR Valve Circuit  Electrical Malfunction

P1401 - EGR Valve Circuit  Short to Ground

P1402 - EGR Valve Circuit  Short to B+

P1403 - EGR Flow Deviation

P1404 - EGR Flow Basic Setting not carried out

P1406 - EGR Temperature Sensor Performance range

P1407 - EGR Temperature Sensor Signal too Low

P1408 - EGR Temperature Sensor Signal too High

P1511 - Intake Manifold Changeover Valve - Electrical circuit malfunction

P1512 - Intake Manifold Changeover Valve Short circuit to B+

P1513 - Intake Manifold Changeover Valve2 Short circuit to B+

P1514 - Intake Manifold Changeover Valve2 Short circuit to ground

P1515 - Intake Manifold Changeover Valve Short circuit to ground

P1516 - Intake Manifold Changeover Valve - Open circuit 

P1520 - Intake Manifold Changeover Valve2 - Open circuit 

P1521 - Intake Manifold Changeover Valve2 electrical circuit malfunction

P1553 - Barometric/manifold pressure signal ratio out of range

Polo Highline 1.9 TDI (9N) 2005

16621 - Manifold Pressure / Boost Sensor (G31): Signal too Low

P0237 - 000 - -

Audi A5 (8T0) 2012 

4166 - Manifold Pressure / Boost Sensor (G31)

P0238 00 [039] - Signal too High

Audi TT 1.8L R4/5VT 

16622 - Manifold Pressure / Boost Sensor (G31): Signal too High

0238 - 35-00 - 

000568 - Manifold Pressure / Boost Sensor (G31): Signal too High

P0238 - 001 - Upper Limit Exceeded - MIL ON

Passat 2.0T R4/4V TFSI 2006 

000568 - Manifold Pressure / Boost Sensor (G31): Signal too High

P0238 - 001 - Upper Limit Exceeded - MIL ON

VW Touran 1.9 TDI

P0236 - Manifold Pressure/Boost Sensor (G31) - Range/Performance Problem/Implausible Signal

Malfunction Indicator Lamp (MIL)(K83) active.

VW Golf 7 1.6TDI 

16622 (P0238 ) - Manifold Pressure/Boost Sensor (G31): Signal too High

16618 (P0234) - Boost Pressure Regulation: Limit Exceeded (Overboost Condition)

Passat 2.0T R4/4V TFSI 2006 

004759 - Pressure Drop between Turbo and Throttle Valve

P1297 - 001 - Upper Limit Exceeded

This MAP Manifold Pressure Sensor aka Boost Sensor aka Thrust sensor  aka G31 is just a  thermistor. Essentially a resistor of a special kind, with the ability to change its resistance  subject to its surrounding temperature, hence the term thermistor is just a  word combination of "thermal" and "resistor".  However G31 sensor may not be fault but rather the wiring harness. Due to the constant engine heat, the harness wiring gets hard and becomes brittle resulting in poor contact, short and open circuits. 

FYI - Thermistors essentially come in two varieties, viz NTC (negative temperature coefficient) and a PTC (positive temperature coefficient). You can quite simply use an ohmmeter to measure the resistance of the thermistor. Then by bringing a hot soldering iron  tip close to the thermistor, its resistance would change in response to the soldering iron's radiated heat. When the resistance increases its a PTC and an NTC when the resistance decreases.  Much like discrete component resistors that are colour coded, thermistors leads are also colour coded which identifies the temperature range they operate at.

CATALYTIC CONVERTER

Catalytic Converter have become a hot topic of late. Thieves are stealing Catalytic converters from parked cars at night. However the Polo Highline 1.9 TDI is known to be troublesome. The main reason for  this being, use of poor quality diesel (500ppm as opposed to 50ppm or even 5ppm) and irregular oil changes  which caused soot build-up to block the performance of the catalytic converter, which in turn may lead to turbo failure.  So its fair to say that it's  not uncommon to remove/replace blocked catalytic converters  to prolong the life of the turbo itself.

However if it's not the Catalytic converter itself causing the above error,  it very possibly not the sensor either even though the diagnostic software may indicate that.  I'd say rather check, repair or replace the wiring harness to the Boost Pressure Sensor (G31) and also check wiring to the Intake Air Temperature Sensor (G42).  See my previous blog post https://volkswagen-polo-highline.blogspot.com/2015/03/wiring-harness-issues.html 

The diagnostic scanners may also thow the following errors in conjunction with the error above,  which could be caused by a leak in Air Intake and or Exhaust

16490 - Manifold / Barometric Pressure Sensor (G71) / (F96): Implausible Signal

P0106 - 35-00 - -

18000 - Altitude Sensor / Boost Pressure Sensor: Implausible Correlation

P1592 - 000 - -

Diesel engines are quite different from petrol engines in the sense that  the diesel engine is not variable in speed or power by controlling the air entering the engine as we do with the  throttle body in petrol styled engines. Feedback from Catalytic converter in petrol engines are also used to adjust the short term and long term fuel trim. Implying that petrol cars also have turbo boost errors due to the cat and intake and exhaust sensors.

16485 / P0101 Mass Air Flow Sensor (MAF) (G70) = Circuit Signal Implausible (out of range)

16497 / P0113 Intake Air Temperature  Sensor-1 (G42) = Signal too High

16515 / P0131 O2 (Lambda) sensor low voltage =  Bank-1 Low Voltage

16584 / P0200 Injector circuit =   Injector Circuit electrical fault

16620 / P0236 Turbo / Manifold Pressure Boost Sensor (G31) = Signal Implausible (out of range)

16622 / P0238 Turbo / Manifold Pressure Boost Sensor (G31) = Signal too High

16683 / P0299 Turbo Boost Pressure Reg = Control Range not reached (underboost) /mechanical fault

16785 / P0401 Exhaust Gas Recirculation (EGR) = Insufficient Flow (blocked)

17055 / P0671  Glow Plug/Heater Cylinder 1 (Q10)  electrical fault, open circuit 

17958 / P1550 code = Charge Pressure Control Deviation

Check for air leaks on both intake or exhaust side 

Turbocharger - check for whining engine and exhaust smoke

Charge Air Pressure Sensor faulty  - check connection to one of the the intercooler pipes

Wastegate Regulator N75 Valve  faulty  - Check one of the 3 thin hoses for leaks

18534 / P2102 Throttle  Actuator Control Motor = Signal too Low, check voltage to accelerator pedal 

18675 / P2243 O2  Sensor Reference Voltage Bank 1, open circuit 

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