P0303 GMC -

Question

P0303 on gmc envoy. code came on once so reset, put in fuel injector cleaner, did not come on for 1000 miles so I cleared it again.please help

Answer 1

P0303 Misfire number 3 cylinder

When it misfire does the CK ENG LT flash? If it does this would indicate a ignition related misfire, and the ignition coil and the sparkplug should be changed, Only a ignition related misfire can flash the CK ENG LT. you may want to swap the ignition coil # 3 with a good known cylinder and if the misfire follows this is definetly a bad ignition coil.