PROBLEMS & DIAGNOSTICS
2015 Chevrolet Silverado 1500 P0420 & P0430 Catalyst Codes
P0420 and P0430 indicate that catalyst efficiency is below a monitored threshold for Bank 1 or Bank 2. They do not by themselves prove a catalytic converter must be replaced.
Confirm the engine, trim, drivetrain, market and installed equipment before using a part number, capacity or repair procedure.
Catalyst-monitor codes
| Code | Monitored bank | Important companion checks |
|---|---|---|
| P0420 | Bank 1 | Misfire, trims, exhaust leak, oxygen-sensor operation |
| P0430 | Bank 2 | Misfire, trims, exhaust leak, oxygen-sensor operation |
A replacement converter should follow confirmation that engine operation and exhaust integrity are correct.
What the codes tell you
The engine computer compares exhaust sensor information to evaluate catalyst performance. Exhaust leaks, ongoing misfires, incorrect fuel mixture and faulty sensor readings can make the monitor report poor efficiency. Repair those causes before replacing an expensive converter, and determine whether the issue affects one bank or both.
What to test first
Record engine and catalyst-related codes, freeze-frame and fuel trims. Inspect exhaust joints for leaks, evaluate upstream/downstream sensor data with the correct test, and confirm there are no active misfires or fuel-control faults. Use VIN-correct emissions equipment and comply with local regulations.
- P0420 identifies Bank 1 efficiency; P0430 identifies Bank 2.
- A flashing misfire warning requires immediate attention.
- Do not remove or bypass emissions-control equipment.
Use the correct model-year manual and current service information. Stop if instructions or safety precautions are unclear, and use a qualified technician for work you cannot verify.
References and further reading
This independent guide is not endorsed by the vehicle manufacturer. Let us know if you spot an error.