why would it appear, stay for a day, then turn off by itself?

 

happens all the time for me.. if you are still nervous about it, just have it scanned.. the DTC code should still be in there.

 

is there anyway to reset the ecu without pluggin it into the code reader?

 

Why would you wan't to do that? If you reset the ECU the code will no longer be there.

 

it turns on and off depends on what kind of codes you are getting. examples if you are experiecing knocking in your engine it will only blink when it detected knocking. my bmw right now is having some issues with charcoal canister and cel goes on and off.

 

i already know what the code is and just want it to reset.

 

it could have been the gas cap CEL. That one turns off by it'self.

 

with gas cap or intake. Post the code if you have it!

 

Disconnect battery resets ECU I think

 

Yah. That one happens to me occasionally.

I thought that was fixed in newer S's?