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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High Speed Computers

HIGH SPEED COMPUTERS

All modern-day motor vehicles using our roads today; and those manufactured since 1996 can literally be referred to as COW ("computers on wheels"). Since your car is less than 25  years in age, it certainly has a computer on board, but the level of control it has over your car is determined by its recentness.  So the more recent your car the more  control the computer has over its functionality. 

BLACK BOXES

However, the computer in question is unlike the ones with the LCD screen, keyboard and mouse that everyone is familiar with, yet very similar in its processing ability. One  could say these computers are akin to the flight recorders fitted to aircraft which in  avionics are commonly called "black-boxes". But unlike the traditional PC, automotive  "black-boxes" are heavily regulated by standards and legislation regarding consumer  safety. 

ECU

Industry wide automotive "black-boxes" are commonly known as Electronic Control Units abbreviated ECUs and is the home of on-board diagnostics software, named OBD II. This  on-board diagnostic system in essence is a combination of hardware and software  running an intelligent system that incorporates various types of the sensors, each  integrated into the vital areas of the vehicle that monitors its overall performance.The most common of which are the engine RPM sensor, the crankshaft and camshaft  position sensors, the car's air and coolant temperature sensor, the oil level sensor, road speed sensor, the accelerator pedal and throttle control sensor which is also  known as drive-by-wire. The software consists of over 100 million lines of code which pools and controls dozens of electronic control units (ECUs) via the CAN  protocol and CAN bus thus able to manipulate everything from Engine Electronics to ABS braking system, to Steering Assist, to Infotainment System, to Heating/Air  Conditioning, to Airbag, to Instrument Cluster, to Tire Pressure Monitoring, to Back-Up Camera among so many other. 

SENSORS

As such, ECUs have revolutionized and souped-up modern motor vehicles, giving them added fuel efficiency, safety, pollution reduction, speed on demand, and an early  diagnostic malfunction detection. Restated, the ECU contains a self-diagnosis system capable of detecting glitches and small mechanical and electrical issues long before  they actually occur thus saving you thousands in tow-in charges and would be expensive repairs. It eliminates the need to cross the fingers when you start hearing  peculiar noises coming from the engine or transmission and it could prevent you from  getting stuck on the road.

DIAGNOSTIC TROUBLE CODES

Vehicle dependent, the OBD II system alerts the driver to any malfunction in real time by flagging errors by way of digital code, displayed on the dashboard. Decoding these  errors timorously and taking the necessary action would certainly avert more serious troubles later. Errors on vehicles without LCD display can be viewed with a diagnostic  scan tool when plugged into its 16-pin ODB II socket. These vehicles would then also have CEL (check engine light) / aka MIL (malfunction indicator lamp, an EPC light among  its menagerie of symbol warning lights. DTC (diagnostic trouble codes) are  essentially fault codes, presented as five-digit alphanumeric codes that identify a particular problem in one of four areas in the car, viz: P-Codes (Power train), U-Codes  (Chassis), B-Codes (Body) and U-Codes (User Wiring Bus Network). 

A few example of these codes are P0195 - Engine Oil Temperature Sensor, P0304 -  Cylinder 4 Misfire  Detected, B1000 - ECU Malfunction, B1713 - Mirror Switch R Down Input Stuck High, C0050 - Right Rear Wheel Speed Circuit Malfunction, C0611 - VIN Information Error,  U0130 Lost Communication With Steering Effort Control Module and U0324 Software Incompatibility with HVAC Control Module. Without a scan tool plugged into the OBD II  socket it’s impossible to extract the DTC from the ECU non-volatile memory, let alone  fix these faults.

ODB II SOCKET

It would therefore be fair to say that the OBD II socket has become the most important and indispensable means of diagnosing automotive problems hence also fair to say that  it has become the most used automotive receptacle since its inception. That being said, OBD II GPS tracker is now also the most convenient vehicle tracking device on  the market via GSM which plugs into a splitter / adapter cable. Armed with a SIM card, the GPS GSM module can be tracked on a cell phone tracking app and the software would even  allow its user to disable the car’s engine remotely via GSM /GPRS and OBD II in the event the vehicle is hijacked or stolen. Unlike GSM where the cost of a data call is  related to the time spent on the network, a GPRS data session is dependent on the amount of data sent and received. So by implication GPRS is “always on always  connected”. 

GPS MODULE

GPS modules generally have several convenient features amongst which is a real-time vehicle tracking system with a 180-day of tracking historical data accessible on a web  server. GPS has time accuracy of 1 microsecond and an accuracy of less than 10 meters. It will continue working even if the cars battery is removed as it has a built-in  180mAh/ 3.7V battery. GSM module also has a host of security features but the best  part of an OBD II GPS Tracker is that it's simple to install without any wire  connections. It is purely a DIY matter of plug and play. A splitter cable that plugs  into the cars original 16-pin OBD II port with two addition 16-pin OBD II ports, one for the GPS module and the other available to a scan tool. 

SECURITY RISKS

All this fancy gadgetry doesn't come with risks. The first of which is the CAN  protocol which suffers from several security issues that were originally ignored by  most vehicles manufactures. Reason being that the various automotive networks and  ECUs were initially designed to primarily gain physical access to the vehicle ECUs and speed / reaction-time was a secondary concern and more important that security which  was then placed on the back burner. With a GSM SIM card in the GPS module that can directly  communicate with the CAN bus and protocol it wouldn't be difficult for a hacker to gain access to the vehicle as it will be just another node on the internet. With remote interfaces like Wi-Fi, Bluetooth, or cellular that is accessible from  outside of the car, access can typically be gained, thus aftermarket OBD-II devices have the potential to introduce security risks to an automobile and compromise the safety of its passengers. Connecting directly to the vehicle in this manner could result in control over safety-critical functions as CAN, by design, offers no  protection from hacker manipulation.

With none existent comms security, somehow cars of the future with a CAN-Bus at its basis doesn't look it has a future at all. It reminds of other technologies that we were forced to abandon with the arrival of the new. Case in point, Vinyl Records for CD recorders, DVD that superseded video tapes, MP3 players that superseded audio cassettes and audio CD's, Flash drives that superseded removable media, etc. Solid state drives that is superseding hard drives. Would we have to abandon our CAN based cars like we did our other techno bits in favour of a new automotive protocols with features that has support for Kerberos, SSH, IPSec, OSPF authentication, VPNs, SSL and TLS?

Limp Mode Scan codes

LIMP MODE

Limp mode has hit car owners like a pandemic, a pandemic that was pre-planned by the automotive industry, knowing full well that most car owners would be at a loss to repair it themselves and that it was  going to be a source of steady profit, a bonanza, a money spinner, a cash cow, a golden goose for them.

Virtually every car owner have experienced the wrath of Limp mode at some time or the other and are often helpless when it happens. Those of you who haven't had the displeasure of encountering Limp mod surely will, its just a matter of time - virtually guaranteed.

STANDARD FEATURE

Limp mode is a standard feature programmed into all post-1996 vehicles to protect their engines and driver / passenger when something goes awry with its EPC system, steering or braking system, etc.  The ever-aware sensing software will activate this feature when it detects abnormal readings from sensors, or compromised mechanical part operations that could potentially cause damage to the vehicle or harm to its occupants.

Every time when Limp mode is triggered the ECU will store a DTC in its non-volatile memory for later retrieval. And since Limp mode can be caused by any of several different engine components, the only way to track down the Limp mode problem is by way of a OBD-II scan tool. Scan tools may be considered the vaccines against this Limp mode pandemic, implying only those who have one will be able to fix their own cars.

ON BOARD DIAGNOSTICS

OBD-II (on-board diagnostics ver2) gave rise to a scan tool market and these scan tools comes in several makes and models, with capabilities ranging from the most basic to the most intricate costing from as little as a few bucks to tens of thousands. Most of the low end scan tools are VW compatible though some are not, whereas all the high end scan tools are compatible to virtually all cars, trucks and bikes.

SCAN TOOL

So, if your a car owner / DIY mechanic, it is imperative to get yourself a decent  aftermarket VW-Audi diagnostic scan tool. If you own an Audi,  Porsche, Bentley, Bugatti, Lamborghini,  SEAT, Škoda or Volkswagen I would suggest that you invest in the USB Cable KKL 409.1 VAG-COM Auto Scanner Scan Tool for VW/Audi (Blue) for starters. This cable supports the ISO9141 and KWP2000 transmission protocols and is usable with VCDS lite downloadable from the Ross tech website absolutely free. I started out with this rig and later bought several dedicated scan tools as well as bluetooth dongles that work with cellphones and software for my tablet. None as good or even comparable to VCDS (VAG-COM) HEX-V2 which surpasses the performance of most generic OBD-II tools, but its VW specific.

ELECTRONIC POWER CONTROL

Limp mode limits the amount of power to your engine and transmission thus delivers poor engine performance. EPC (electronic power control) may be lit and Malfunction Indicator Lamp (MIL)(K83) may also be lit. 

Limp mode scan codes:-

000289 (P0121) - Throttle Position Sensor (G69): Implausible Signal

000290 (P0122) - Throttle Position Sensor (G69): Signal too Low

004243 (P1093) - Bank 1; Fuel Measuring System 2

000545 (P0221) - Angle Sensor 2 for Throttle (G188): Implausible Signal  

000808 (P0328) - Knock Sensor 1 (G61) Signal too High - Intermittent

05445 (P1545) - Throttle valve control system, Malfunction

05464 (P1558) - EPV throttle Drive - G186, Electrical malfunction in circuit

01314 - Engine control module / No Communications

17252 (P0868) - Transmission Fluid Pressure Adaptation at Limit

             

WIRING HARNESS

As can be seen from the above, all these Limp mode scan codes / faults are associated with a VW wiring  harness problem and is normally a connector problem but it can also be the a failed throttle body, a knock sensor, the torque circuit, a brake light. The gears inside of the throttle body can strip or becomes clogged with dirt. Remember the last resort is a failed engine control unit (ECU).