Main Catalyst Efficiency Below Threshold (Bank 1)
What does P0422 mean?
The P0422 code means the vehicle's onboard diagnostic system has detected: Main Catalyst Efficiency Below Threshold (Bank 1). This is a moderate severity code.
Common Symptoms
- Check Engine Light illuminated
- Sulfur smell from exhaust
- Reduced fuel economy
- Failed emissions inspection
- Possible rattling from catalytic converter
Probable Causes (Ranked by Likelihood)
- Worn or contaminated main catalytic converter Very High
- Engine running rich due to fuel system issue High
- Exhaust leak upstream of downstream O2 sensor Moderate
- Faulty downstream oxygen sensor providing false readings Low
Step-by-Step Diagnostic Procedure
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Monitor upstream and downstream O2 sensors on Bank 1 -- if downstream mirrors upstream switching, the catalyst is failing
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Check for exhaust leaks with a visual inspection and by listening for hissing
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Verify no active misfire codes that could cause catalyst damage
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Check fuel trims for signs of rich running that could contaminate the catalyst
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Tap the catalytic converter and listen for rattling of broken substrate
Frequently Asked Questions
Can I drive with code P0422?
Yes. The vehicle drives normally with a failing main catalyst. Emissions output increases, so you will fail an emissions test. Extended driving with a failing cat will not damage the engine.
How much does a catalytic converter replacement cost?
OEM catalytic converters range from $300-$1200 for the part alone. Aftermarket options are available for $150-$500. Labor typically adds $100-$300 depending on accessibility.
Can I use a universal catalytic converter?
In many states, a CARB-compliant aftermarket converter is acceptable. However, California and some states require specific CARB-certified converters. Check your local regulations before purchasing.