1998 Chevrolet Pickup 4.3L Engine P0302 and P0420 Codes: Causes and Fixes
I own a 1998 Chevrolet Pickup with a 6-cylinder 4.3L engine. My vehicle failed an emissions inspection because the battery had been dead for some time, resulting in loss of stored computer data. On my way home, the "Service Engine Soon" light activated. I scanned the system and found two diagnostic trouble codes: P0302 and P0420. After disconnecting the battery for only 2 minutes to reset the codes, I reconnected it — but the check engine light immediately came back on. When I restarted the engine, both codes persisted. What do these codes mean, and what steps should I take to fix them? I'm looking for accurate technical explanations and repair guidance based on my vehicle's specifications.
P0302 typically indicates a misfire in cylinder #2. This misfire can lead to incomplete combustion, which may cause the catalytic converter to become less efficient — potentially triggering P0420, which points to a catalytic converter performance issue. For more details, refer to OBD-II code explanations: https://www.obd-codes.com/p0302 and https://www.obd-codes.com/p0420. Avoid repeatedly disconnecting the battery — doing so can corrupt stored data and prevent proper diagnosis or passing emissions inspections.