P0420
Moderate
Powertrain
Catalyst System Efficiency Below Threshold (Bank 1)
Common Causes
Degraded or failed catalytic converter
Failed downstream oxygen sensor
Exhaust leak before or at catalytic converter
Engine burning oil or coolant
Incorrect fuel type or contaminated fuel
Quick Info
| Code | P0420 |
| System | Powertrain |
| Severity | Moderate |
Disclaimer
This information is for diagnostic guidance only. Always verify repairs with a qualified technician before performing safety-critical work.