EPC and Engine Check Light on - Any advice?

[RMC83]

Hey guys,

Well...i've got a bit of an issue...

Took the car out for a blast last weekend, all seemed fine & no issues, but today, i started it for the 1st time since last weekend & the EPC and engine check light have come on. They both came on as soon as the car started. The car is rough on idle & is limiting itself to 2k rpm (i guess limp mode). I did not take it out for a drive, but did move it, only around 50m or so to see if anything else could be noted & have noticed that the brakes are very squeeky, just when slowing from tickover speed to a stop.

I checked coolent level & still full & there isnt really any more white smoke coming out the back either than i can notice.

I dont have a Vag Com & it's public holidays over here in Asia, so i'm having to wait until Tues. I have a local german car specialist located just 10mins walk from my house, so i will take it there on tues to get diagnostic check done & just have to take things from there.

Any idea's what this could be, based on symptoms above? It seems stange that it was completely fine last weekend on a 3hr drive, then this happens when starting it for the 1st time since last weekend.

I looked through some previous discussions & i guess it could be a range of things from a sensor, a sticky injector, hpfp, plugs, coil. What about the brakes, could an ABS sensor or some brake issue cause the error that puts the car in limp mode, which then makes the idle rough? I'm just thinking out loud really just now, as i dont have the error codes yet in order to narrow it down.

Thanks in advance.
Roy

[RMC83]

Also...something else i noticed today is that the engine oil smells of petrol & seems to be less viscous, so it seems petrol has managed to mix with the oil.

What would this usually point to as the problem, a stuck injector in the open position?

Cheers
Roy

[welwynnick]

I think you would be lucky to find the fault by guessing, though I doubt it's anything to do with the brakes. The CEL usually comes on because the ECU has been able to detect a fault that would cause a significant increase in exhaust emissions, which really means any fault in the engine management system like fuel or ignition control. Its often down to misfire detection. If that was the case, a cheap OBD2 reader might be able to read which cylinder was at fault. That won't tell you the cause, but you could at least look at the spark plug and associated wiring. You really need to get the error codes read properly using VCDS.

Nick

[RMC83]

I think you would be lucky to find the fault by guessing, though I doubt it's anything to do with the brakes. The CEL usually comes on because the ECU has been able to detect a fault that would cause a significant increase in exhaust emissions, which really means any fault in the engine management system like fuel or ignition control. Its often down to misfire detection. If that was the case, a cheap OBD2 reader might be able to read which cylinder was at fault. That won't tell you the cause, but you could at least look at the spark plug and associated wiring. You really need to get the error codes read properly using VCDS.

Nick

Hi Nick,

Thanks & yes...without the codes, it's a needle in the haystack job. The car's going in to the garage tomorrow for the Vag Com check, so hopefully i'll have some better info tomorrow.

I knew i should have bought an OBD2 reader when i got the car. Anyway, I have bought one online now (for the next time), for now though...i'll just have to see what tomorrow brings when.

Cheers
Roy

[RMC83]

I managed to get a Vag Com check today, the error codes are P0601 and P1923, so it seems to be something electrical. There was no mis firing or low rail pressure codes etc, the guy with the Vag Com said there were no errors relating to mechanical issues & he thinks it's either the ecu or the remap that's caused the issue. The car is back with the guys that did the tuning now. They were closed today...but at least i managed to get the error codes today & they will check again tomorrow & we'll take things from there.

Has anyone had to replace an ecu? I believe we use MED9.1 & it's the same as other VW & Audi models, so just wondering if it's the ecu that dead, i wonder if anyone else has had the same or similar issue & any idea what caused it?

Cheers
Roy

[RMC83]

Error code details attached for reference.

Cheers
Roy

[Jim Haseltine]

A checksum error. I dislike pointing fingers but that shouts 'remap' to me. To quote a guy I used to know who was weird enough to enjoy digging into assembler code, maps and EPROM flashing - "They say it's the ECU. It's NEVER the ECU". I think 'NEVER' was an exaggeration - 'rarely' would have been a better word.

[welwynnick]

"They say it's the ECU. It's NEVER the ECU". I think 'NEVER' was an exaggeration - 'rarely' would have been a better word.

My brother used to work for Motorola at the plant that manufactured ECUs. He said they were always getting ECU returns, and 99.99% of the time they were no fault found. It was ALMOST always everything else that interfaces with the ECU that was at fault.

Checksum error might sound like a tune problem - but what would have changed between no-fault and fault? If the tune was at fault, wouldn't the light have been on all the time?

Nick

[IanH755]

Checksum error might sound like a tune problem - but what would have changed between no-fault and fault? If the tune was at fault, wouldn't the light have been on all the time?

As we don't know what type of tune was done nor by whom the new map "may" have pushed a parameter right up a limit and the cars just tipped that limit to put the ECL on, as a suggestion.

[welwynnick]

I've had a few similar tune-related problems over the years:

1) In one instance I had a fuel control adaptation parameter pushed to the limit, and it caused errors but no misfires or CEL. I think I fixed it with new lambda sensors.
2) Sometimes a turbo tune pushes the coil pack to the limit unless you fit plugs with smaller gaps, which I had to do once.
3) The extra boost can cause leaks in the charge air pipes, and I got misfires at WOT peak torque revs and a very sudden misfire and limp home. Took a while to fix, but it went away completely with T-bolt clamps instead of jubilee clips on the charge air coupling pipes.
4) "Implausible transmission ratio"

Those are just my experiences, so I think there are all sorts of things can go wrong with tuning.

Nick