P0423
PowertrainCatalystmoderate severityHeated Catalyst Efficiency Below Threshold (Bank 1)
What P0423 Means
The PCM detected the heated catalytic converter on bank 1 is operating below efficiency thresholds. This reduces the converter's ability to clean exhaust gases.
Symptoms
- Check engine light on
- Failed emissions test
- Sulfur exhaust smell
Common Causes
- Failed heated catalyst
- Faulty O2 sensor
- Catalyst heater fault
- Exhaust leak
Diagnostic Steps
- Scan and confirm P0423
- Review O2 sensor data
- Check catalyst heater operation
- Inspect exhaust system
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