Engine Error
P0423
Heated Catalyst Efficiency Below Threshold (Bank 1)
Severity
Medium
Symptoms
Check engine light, rotten egg smell from exhaust, failed emissions
Common Causes
- Failed heated catalytic converter
- Faulty O2 sensors reading incorrectly
- Exhaust leak near the catalyst
- Engine misfire destroying the cat
How to Fix
- 1 Replace heated catalytic converter
- 2 Test and replace O2 sensors
- 3 Repair exhaust leak
- 4 Diagnose and fix engine misfires
Estimated Repair Cost
USD
$400
–
$2500
Catalytic converter replacement: $500 - $2,500