Is it possible that AutoZone or somewhere could still find a thrown code even if the check engine light is not on??? I have been told both yes and no...anybody know for sure or from experience??

 

Yes, for many drivability codes the SES light will turn off after a set number of trips or starts, but the code must remain stored in the ECU.

This is especially common with evap leaks, misfires, etc.

 

yes it is possible. 4th gens get a ghost code for the knock sensor and it should not be any different for ours. sometimes the knock sensor will trip when another malfunction is detected but it can occur independently. when it goes bad, the ecu will retard the timing and cause diminished performance.