P0422
PowertrainCatalystmoderate severityMain Catalyst Efficiency Below Threshold (Bank 1)
What P0422 Means
The PCM determined the main catalytic converter on bank 1 is not reducing emissions efficiently. This is usually judged by comparing upstream and downstream oxygen sensor readings.
Symptoms
- Check engine light on
- Failed emissions test
- Reduced fuel economy
Common Causes
- Failed catalytic converter
- Faulty downstream O2 sensor
- Exhaust leak
- Engine misfire or fuel issue
Diagnostic Steps
- Scan and confirm P0422
- Compare upstream and downstream O2 data
- Inspect exhaust for leaks
- Test catalyst efficiency
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