EPC on dashboard

[david7m]

Have just been out to fill up, on way home I was cruising at 50mph in sixth through camera's on cruise control, then went down to 30 for more camera's, then pressed resume in fourth. It picked up to about 45 mph, then backed off, and EPC light came on dashboard. So pulled over, it then went really lumpy. So I turned it off.

Left it 2 minutes, then started it with no problems. Light did not come back on either!

Have just checked manual, and it said it went lumpy because it had detected an engine fault, and automatically went to a different programme. Not too sure though, because it's chipped !!?!?!!?!?

It also says to take to dealership without delay. Is it ok to drive to work tomorrow and try to get to dealership at lunchtime?

Has this happened to anyone else?

[PhilT]

Have you got VAG-COM or anything similar?

[david7m]

Nothing at all.

Was hoping that because the light has gone off thats it ok ! But its probably not.

I thought that maybe pressing resume in a different gear has 'confused' it ??????

[Joshie]

This has happened before on my S4.

I was driving home and the yellow EPC light came on as the engine revs fell to tickover. Pressing the accelerator had no effect. I reluctantly switched off the engine and when I started it again everything was back to normal.

I read the handbook like you and realised that the ECU had switched to the secondary programme - whatever that means.

But the phenomenon never repeated itself again. So I'd keep an eye on it to see if it does but it is probably just a one off anolmaly in the ECU.

[Dippy]

This is exactly why VAG-COM is such an investment. AFAIK the 'secondary programme' is just a reduced boost map (aka 'limp' mode). There are a number of triggers for this, and you need to know what caused yours.

It happened to me last year and the cause was simply a low temperature reading on my one of my pre-cats. It was just a sensor problem which AmD fixed at my last service.

My case is one of the 'safe' triggers. They are the ones that affect emissions. I.e. if my cats are not up too temperature, my emissions will be too high, so boost is retarded to protect the environment (and not the engine).

However there are other triggers such as lean burn or boost pressure discrepancies which enter the limp mode to protect the engine. This is what happened to Ian.

If it keeps on happening then you do need to get it diagnosed. Personally if it were me I'd want to see the DTC anyway for peace of mind.