EPC Q & A CONTINUED
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.
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 will trigger the malfunction indication lamp (MIL) and the car would also smoke profusely, since the ECU cannot achieve the required stoichiometric ratio and trigger a DTC P1101 in memory. If the ECU supports failure mode effects management (FMEM) the ECU 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 .