The P0421 trouble code is associated with Warm Up Catalyst Efficiency Below Threshold (Bank 1), indicating that the warm-up catalytic converter in Bank 1 is not operating as efficiently as expected during the warm-up phase.
Warm Up Catalyst Efficiency Below Threshold (Bank 1)
Code symptoms P0421.
1. Illuminated “Check Engine” or “Service Engine Soon” light on the dashboard.
2. Decreased fuel efficiency.
3. Lack of power during acceleration, especially during the warm-up period.
This code is common in brands such as:: Chevrolet, Renault, Ford, Toyota, Nissan, Mercedes Benz, Honda.
Causes of the code P0421.
1. Faulty warm-up catalytic converter in Bank 1.
2. Oxygen sensor issues.
3. Exhaust leaks.
4. Engine misfire.
5. Problems with the Engine Control Module (ECM).
Code Solutions P0421.
1. Check and, if necessary, replace the warm-up catalytic converter in Bank 1.
2. Inspect and replace any malfunctioning oxygen sensors.
3. Repair any exhaust leaks in the system.
4. Address any engine misfire issues.
5. If ECM issues are suspected, consult a qualified technician for diagnosis and potential reprogramming or replacement.