EPC Q & A CONTINUED

EPC Q & A CONTINUED

It appears that more and more VAG drivers are experiencing Limp Mode with their VW, Audi , SKODA and SEAT vehicles and it appears that service agents are not as competent as expected. This urged me to present 3 more limp mode cases on a VW Beetle, VW Golf and a Golf TDI for the benefit of those with similar vehicles.

Question?

Hello my name is Mariiam Lopez. I have a 2002 VW beetle. I had been having problems with my car for more than a year. First started with the EPC LIGHT on, I had it on for a few weeks and it came and went, but then my car started to lose power while driving. I had to park and turn it off. I would wait a few minutes and then I started it again and the light went off . But then the EPC light stayed on and the speed didn't go up 10 miles (limp mode). I went to a mechanic and he said it was the throttle body. I had it changed. Two days the EPC LIGHT got on again. I took it again to another mechanic and he said it was the accelerator sensor. I change it and I even got the pedal. Next week got the EPC LIGHT on. It was driving regularly until it didn't want to turn on. I let my car rest for more than two months. I stared using it for a few weeks now and the EPC LIGHT goes on and off when I turn off. Now while driving in the freeway my car lose power and I have to park and let it rest for a few minutes and it drives fine but after a few minutes EPC LIGHT turns on. Now my car turns off in the middle on the freeway and all the lights on the dashboard are on. I park and turn on again but I have to accelerate in order to make my car work. Also the red oil light goes on and beeps when EPC light is on. My car has the same radio. Thanks

Answer!

Hola Mariam como estas? I so sorry to hear that you've had so much trouble with your VW Beetle and for such a long period of time. I can relate to what you are going through every time you need to go somewhere, especially at night when you have to drive a car that is completely unreliable. Considering that two mechanics, both of whom guessed that your throttle body and your accelerator sensors were faulty and that both parts were  replaced and your Beetle is still faulty, makes you saint with the patience of biblical Job. But your mechanics are not alone, so many VW service agents replace parts on Beetles and other VAG vehicles on a regular basis which often doesn't fix the problem, making car owners constantly despondent with VW and their "technical personel". At this point in time  I would be very hesitant to suggest that you replace any component without a diagnostic scan of your Beetle. It would have been great if you can get a copy of your Beetle's scan from one of your mechanics and upload it, so that I can  properly analyse it. Mind you, the data in group 60 - group 66 would  really be helpful to determine whether or not the adaptation was successful.  The EPC light problem can be caused by some many things and in your case its not your radio. So I suggest you check the fluid levels of your oil and coolant and make sure the coolant isn't leaking from reservoir bottle onto the wiring harness, if it does, the instrument panel is bound to malfunction. Also check that your fuel cap seals properly and check the vacuum hoses from the brake booster to the secondary air inlet valve and the hose to the combi valve. If this doesn't solve your problem, read through some of my other blog pages to get a better idea of what must be checked. I don't wish to scare you but Beetles especially MY2000 are well know for electrical problems and catching alight with the flames originating from underneath the firewall,  burning its way up the wiring harness, melting the fuse block on top of battery. So do take care.

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Question?

Hello my friend. I'm Charles Gunn and I have a VW golf mkv fsi 1.4 2005, which I bought in December of 2007. Since I bought her, she's been going into limp mode when I least expect her to, and have had this problem for the past three years. In my endeavours to fix it, I've tried so many garages, non of whom  could help. Worst of all a VW dealer charged me well over £1200, for replacing the wrong components, making me go back and forth to them, yet they never sorted out the problem. Furious... My VW golf goes into limp mode regardless of weather conditions and especially on long drives and on the motorways whenever I exceed 100kph. I found switching off the engine and letting it cool before staring helped but this was temporary because when it becomes hot, limp mode returnes. She frequently lost power when going up hill or on an incline to a bridge. I've done lots of internet  research and tried most forums but no luck. Thus far I've replaced the NOx sensor, MAF sensor, four coil packs and a fuel rail pressure sensor and an air filter. I spent over £1500 and still have a limp mode problem. Can you please help me? The fault that showed up on the scan is; 

1 Fault Found 
16575 - Fuel Pressure Sensor (G247): Implausible Signal 
P0191 - 008 - Implausible Signal - Intermittent 
Readiness: 0000 0000

Answer!

Hi Charley, I must commend you for your perseverance and for your gusto to kick limp mode's ass. Three years of limp mode is probably more than most people can bear. Anyway I see that you replaced a NOx sensor even though your Readiness is 0000 0000. A faulty NOx sensor would have interfered with your short term fuel trim, which would have resulted in a 0010 0000 readiness. A faulty MAF or air filter would also  have also interfered with your readiness which would have resulted in 0001 1000 reading. I'm so sorry to say that you replaced these items, because according to your readiness monitors they are not he cause of your troubles. The coils you replaced can cause limp mode but would also causes the engine to vibrate and idle poorly which would have also given you a P0300 (misfire) error code, so I think they were also replaced unnecessarily. The fact that you replaced the fuel rail pressure sensor says that your were definitely on the right track as pointed out by theP0191 fault, which may have been faulty hence sending intermittent signals to the ECU. However I am more inclined to think that your submersible fuel pump inside the tank is the culprit since it is responsible for creating the fuel pressure, which  is absolutely necessary to drive the injectors. But before you replace the pump, monitor the voltage supply to the pump since corrosion on the fuse in the fuse box that supplies the fuel pump voltage could cause a very similar symptoms.

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Question?

Hi, I need your advice  and please go easy on me because I'm a woman, who  knows very little about cars.  I have a Vw Golf GT TDI 2.0 with 81000 miles on the clock, which I bought about a month ago and it goes into limp home mode, whenever I get to about 70 mph and 3000rpm's but it comes right  when the engine is turned off and back on again. The local garage  ran a dianostics check and they suggested that I either put some diesel cleaner into my tank or use cleaner diesel as they think it's the turbo sensors that  gets clogged-up with soot! I've done some internet research and forums suggested I check the MAF.  So yesterday i drove the Golf untill it went into limp mode, then I switched off the engine and unplugged the MAF.  I could feel that the turbo wasn't working, not as responsive as it usually is. Anyway I drove upto 75 mph, when limp mode usually kicks in. Nothing happened and I increased my speed to 85mph and limp mode still didnt make an appearance. I stopped the Golf, switched off the engine  plugged MAF back in and sure enough limp mode kicked in at 75mph, do you think I need to change the MAF or could it be something else causing the problem?

Answer!

Hi there. It really would have been great if you had a diagnostic scan from which to work but since you don't have one, analysis is bound to be difficult and probably inaccurate. A MAF sensor can cause a limp mode home fault but it doesn't not mean it is faulty in your case. By disconnecting the MAF sensor the OBD System Component Monitor would immediately determine that the  mass airflow  sensor circuit voltage is outside an acceptable range. Thus One of two things could happen:-

1. The ECU will prevent the car from starting.
2. The engine will start but may trigger the malfunction indication lamp (MIL) and the car would also smoke profusely. Since the ECU cannot achieve the required stoichiometric ratio, it will trigger a DTC P1101 in memory. If the ECU supports "failure mode effects management" (FMEM) it will  default to a ‘safe’ mass airflow value, allowing the the vehicle to be driven to workshop for repair. Somehow I think you may not have unplugged the MAF but it is worth your while cleaning the MAF but be careful not to damage the wire inside.  Since  your car is Diesel I somehow doubt that is would be the MAF .

Question?

Nazeem Sterris. Hi.I have a polo 1.4 16v bby.problem is epc light stays on. It starts well.revs up well but has a slight miss fire when idling.after couple of minutes of idling it goes into a limp mode where revs go up to 1500rpm and pedal don't work. Pls help

Answer?

Hi Nazeeem. The slight miss you are describing is most likely the cause of your EPC problem. Sorry, I cannot pinpoint the problem for you because  you don't have a diagnostic scan attached, I'm guessing that the miss could be associated with your Ignition Coils, your Fuel Injectors,  or your Throttle Body, or your Fuel Pressure Regulator Valve or even your Wastegate Bypass Regulator Valve. You need to work through them systematically but first check that your fuel cap seals because if it doesnt, the EVAP pressure cannot stabilize  and can also trigger the EPC circuit.