cyberorth

What do you stock guys and ladies do with a disappearing CEL. I had one this morning along with a rough weak idle. Restarted the car and it was gone.
Thanks

Sbpsu354

I had an A7 with a strange electronic parking brake fault. The failure message would clear itself, so when it would pop up, I took pics of it on the dash which included the date and time. My local dealer has an excellent service advisor that took care of me, so it wasn't really an issue, but it helped to focus the diagnostics and provided proof of the issue.

mister2d

Use a OBD2 scanner so that you can get the exact fault code. There's no guess work this way. Mine was a persistent misfire on the same cylinder. It had a rough idle and went into limp mode. Twice I turned it into the service department and the second time they replaced the ignition coil that kept throwing the error.

Your situation could be different, so I would start with a code reader.

abcut973

^ Correct! No second guess on a CEL. Either you know or you don't. Get you an OBDII reader and check the fault codes whenever it happens. That will be a good start for troubleshooting. If you are mechanically inclined you could deal with it or let the dealership taking care of it. But at least you have an idea of what the issue can be.
Rough idle can be misfire but also can be the result of different root causes. GL

cyberorth

So far only once and right after a fill up. I have had about 60 miles or so since.

MarkC63

Just had this happen to me tonight on the drive home. Driving in Comfort in slow moving traffic. Idle went rough, RPM's dropping low. Then the CEL light flashes and stays on. Continued to drive home and the car was fine - but didn't push it. Turned the car off and turned it on again. CEL light still on. Left it a couple of hours and turn it on again - CEL light still on. Let's see what happens in the morning, but looks like I will be dropping it at the dealer to see what the problem was.
I have had a rough idle about 3 times leading up to this - but it never resulted in the engine light coming on.
Might need to invest in a OBD2 reader. Has anyone tried the bluetooth ones that connect to phone apps. Are they any good? Any recommendations?

MarkC63

Took the car into the dealer today. Apparently their is a software update that they believe will fix this issue. Engine upgrade and transmission upgrade getting done. Will update once I get it back.

Mbm6f

My W204 was triggered by some winter blend gas with the EC tune. Get it checked, and is the W205 the same in that if it is flashing get it towed and checked right away?