Engine Error
P0422
Main Catalyst Efficiency Below Threshold
Severity
Medium
Symptoms
Check engine light on, sulfur/rotten egg smell, failed smog check
Common Causes
- Failing main catalytic converter
- Exhaust leak before catalyst
- Engine burning oil or rich condition destroying cat
- Aging downstream O2 sensor reading falsely
How to Fix
- 1 Replace main catalytic converter
- 2 Repair exhaust leaks
- 3 Fix underlying engine misfire/rich condition
- 4 Replace downstream O2 sensor
Estimated Repair Cost
USD
$400
–
$2000
Catalytic converter: $500 - $2,000