Diagnostic Aids
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. 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-Refer to Symptoms - Hydraulic Brakes in Hydraulic Brakes.
- Drive shaft not balanced-Refer to Vibration Analysis - Driveline in Vibration Diagnosis and Correction.
- Worn or damaged accessory drive belt-Refer to Symptoms - Engine Mechanical in Engine Mechanical.
- There may be more or less cylinders actually misfiring than indicated by the scan tool.
- Spray water on the secondary ignition components using a spray bottle. Look and listen for arcing or misfiring.
- If there are multiple misfires on only one bank, inspect the fuel injector and ignition coil, power and ground circuits for that bank. Refer to Engine Controls Schematics .