Driving some back country NorCal roads today (very bumpy and throwing the car around quite a lot) mostly in 3rd gear in sport mode (I've got the V8 btw) at the upper end of the rev range but nothing super aggressive when the engine trouble warning light started flashing and the engine sound changed quite noticeably. Warning light stopped flashing after approx 10 secs and all looked good except engine note was very different. Seemed muffled but yet at same time had a deeper throb. Got car home ok and my perception was the performance was lost a bit although I baby'd it home so didn't try anything other than coast it home. Switched engine off and let it sit for a minute, started it again and back to normal? Took if for a drive and all good?
Anything to worry about? Could I have jolted the engine into thinking it had a problem some how and then it reset when I cycled the ignition? Just wondering if someone here knows what happened rather than book it in with the dealer?

 

I assume you're talking about a check engine light. Many things can set that off, but if it reset quickly, as you said, and all now seems normal, I wouldn't take it to the dealer just yet. If it happens again, yes, but without a current problem, the dealer would likely tell you all is well.

 

A code reader, dealer or elsewhere, may let you know what happened, as long as the 'issue' was stored.
Lawrence

 

An OBD II code reader will only let you know what codes a sensor triggered, but not necessarily reveal the cause, especially when the check engine light comes on and then resets quickly. Sensors sometimes malfunction or trigger for reasons other than their intended purpose.

I had a recent experience with that in my wife's car, which had been showing a check engine light 3-4 times sporadically over the last couple of months, and had always quickly cleared. Otherwise, all was normal. Last week, the check engine light stayed on, and I plugged in my code reader, which showed 3 seemingly unrelated codes. We took it to the dealer, who found a cause I never would have suspected.

Her car has shutters behind the grill that open and close depending upon how much cool air is called for. It makes the car more aerodynamically efficient with them closed. Turns out the shutters were bumping into a branch of the wiring harness because of a loose clamp, which was triggering random sensor warnings. There is no code for that, and it was a great piece of detective work on his part plus a very simple fix, but he never would have bothered to track it down had the check engine light been off.

Again, if your warning light comes on again, I'd take it in, otherwise, I wouldn't worry about it until then. Generally speaking, a dealer won't do anything if there's no active problem indication, except perhaps to check for an old code and then say, "everything seems fine now."