EPC light at track day

[martz]

hi guys I was out on the racetrack going pretty hard and an EPC light came on and it cut a lot of power (limp mode?). There's also an error message on the screen that says:

"Start-stop system:
system fault!
Function unavailable"

Anyone experienced this or know what the go is?

[S4Per]

Get codes via Vagcom. Can't really troubleshoot much without those as a starting point.

[martz]

will take to shop on Monday...

[AudiA6A5]

We're you very low on gas? Had this happen once when low on gas, going down hill, and floored it. As soon as I floored it, the EPC came on and the car went into limp mode so I pulled over. Restarted the car and EPC was gone. Drove home, checked AZ and found same thing happened to someone else. Never happened since.

[martz]

nar the tank was almost full. Started the car today and EPC light is still on. Anyway I'll found out tomorrow, hopefully nothing serious.

[InvigR8]

Even if you don't have access to a VAGCOM, you can use a generic OBD-II reader to see if a fault (or a few faults) occurred. That is, if you are curious to know what it might be before brining it into the shop.

[cmg_r]

EPC light in this case could be linked to a cylinder misfire if you drove in "aggressive" mode :).

If this is the case you might have the following situations:

- just a software issue that triggers the error (cylinder misfire) that can be corrected by erasing the error with VAG-Com, VAS, etc.

If this is not the case then

- a spark plug or coil pack error (you must replace one or another or better replace both of them just to be sure).

Because of the cylinder misfire error the cylinder is disabled and the auto-start system is disabled as well.

Hope this helps!

[martz]

Thanks CMG, I have passed on that info to shop. There were a few errors that came up and one of them was the cylinder misfire so you very well could be right. What caused it though is concerning to me. Will this keep happening if I take the car out on the track?

Edit: Here are the faults that came up:

Underboost fault
Cylinder 5 misfire
intake air temp sensor fault

[cmg_r]

You are welcome. Hope you will solve the issues and enjoy the car again in no time. There seem to be more things happening there. If all errors are intermitent and can be deleted you might be fine, but i would make some more tests ( pushing the car hard several times). If the errors persist or reappear i would change the air sensor and the coilpack+spark for cylinder 5. I don't know if and how much the underboost error is linked or the cause of the others.

As if it happens again, it might, at least the missfire. As i was told, once you keep pushing the car hard ( race track, aggresive continuos driving) the coilpack/s and/or sparks become somehow "consumables" :). If your car is stock they should not give you problems, this is more probable if your car has power upgrades. Eventually if these errors are caused by the coilpack/sparks you could change them all just to be sure you reduce/eliminate the risk of this happening anytime soon.

As far as i know the OEM coilpacks and sparks are the best you can get ( but i might be wrong) :)

Hope this helps.

[martz]

I have the car booked in for Monday to pinpoint what's gone wrong, keep ya's posted.

[ChrisMF]

Hey Martz! I had the EXACT same thing happen to me today. full speed 5th to 6th gear, BAM! EPC light came on, felt like my car was running with a cylinder or two turned off. Tried cooling her off, restarting, driving around at 25mph, stopping, restarting. EPC still there. Drove 100 miles home smooth as ever, but it's definitely in limp mode. Going to get a VAGCOM and run it this week...

Were you able to figure out what was wrong with yours?? Did the dealer give you any grief over it? I'm running EPL Stage 1 on my 2013 S6.

[flyfishing]

I had this with EPL stage 1. I was flooring it and driving hard. It occurred. Then I restarted. It has NEVER recurred again :) It's been a long time.

[BWilson]

I have the car booked in for Monday to pinpoint what's gone wrong, keep ya's posted.

What did you find out that was wrong with your car?

[ChrisMF]

Not sure about Martz... But my EPC light was actually a bad diverter valve, getting it replaced, hopefully no issue after.

Sent from my Pixel using Audizine mobile app

[jkintzy]

Not sure about Martz... But my EPC light was actually a bad diverter valve, getting it replaced, hopefully no issue after.

Sent from my Pixel using Audizine mobile app

Bump. Any fix after limp mode epc after running the car hard?

[FourRings115]

You are welcome. Hope you will solve the issues and enjoy the car again in no time. There seem to be more things happening there. If all errors are intermitent and can be deleted you might be fine, but i would make some more tests ( pushing the car hard several times). If the errors persist or reappear i would change the air sensor and the coilpack+spark for cylinder 5. I don't know if and how much the underboost error is linked or the cause of the others.

As if it happens again, it might, at least the missfire. As i was told, once you keep pushing the car hard ( race track, aggresive continuos driving) the coilpack/s and/or sparks become somehow "consumables" :). If your car is stock they should not give you problems, this is more probable if your car has power upgrades. Eventually if these errors are caused by the coilpack/sparks you could change them all just to be sure you reduce/eliminate the risk of this happening anytime soon.

As far as i know the OEM coilpacks and sparks are the best you can get ( but i might be wrong) :)

Hope this helps.

This. Stock, you should be fine with hitting the track. I have done as many as 5 track sessions in a day in northeast summer heat and never had a problem. But I am stock. The C7.1 with a tune is the most common car to have serious issues and even the dreaded blown turbo that so many on here talk about. I am C7.2 and stock and it’s dead reliable. Good luck!

EDIT: just saw dates of old post. Oh well.