Diagnostic Aids

WARNING: This page is about a different car, the 2003 Cadillac Seville and 2003 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.

Excessive vibration from sources other than the engine could cause DTC P0300 to set. The following are possible sources of vibration:

Variable thickness brake rotors. See appropriate article in BRAKES.
Worn or damaged accessory drive belt.

If there are multiple misfires on only one bank, inspect the fuel injector and ignition coil, power and ground circuits for that bank.