One problem related to check engine light on has been reported for the 2004 Chevrolet Cavalier. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2004 Chevrolet Cavalier based on all problems reported for the 2004 Cavalier.
Idle miss while auto is in gear (automatic). Initial occurrence 15000-20000 miles. Started when at a stop light you could feel the miss it was every 30-45 seconds. No check engine light associated with problem. Has gotten worse, still no check engine light. Now it stalls and you can watch the tachometer drop 25-50 rpm. Took it to the dealership under extended warranty @ 512010 miles. Dealership said it was #2 cylinder misfire. Changed ignition module & coil pack. I picked it up and drive it 1. 5 miles and it was the same. Took it back and they swapped injectors with another cylinder and spark plugs, changed fuel filter. Picked it up again. Same problem. Dealership said they cannot fix it until there is a check engine light, even though problem could be duplicated every time car was taken back to the dealership. I had the service writer and the actual mechanic in the car with me each time and they agreed there was a problem. As of this date 1-18-10 problem still exists.