Catalyst Efficiency Below Threshold (Bank 1)
The P0422 code indicates that the catalytic converter on bank 1 is operating below its expected efficiency threshold. The oxygen sensors monitor the converter's ability to store oxygen; when the rear sensor's signal mimics the front sensor's signal, it suggests the catalyst is not effectively reducing emissions. This can be caused by a failing converter, exhaust leaks, or sensor issues.
01. Most Common Causes
- Faulty catalytic converter
- Exhaust leak before or after the converter
- Oxygen sensor malfunction or contamination
- Engine misfire or rich fuel condition damaging the catalyst
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Failed emissions test
- Possible decrease in fuel economy
- Rotten egg smell from exhaust (if converter is failing)
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Inspect exhaust system for leaks or damage.
Step 3: Monitor oxygen sensor data with a scan tool; compare front and rear sensor readings.
Step 4: Perform a catalyst efficiency test or use a propane torch to check for converter blockage.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, but the vehicle may fail emissions and fuel economy may suffer. Prolonged driving could damage other components.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Replacing a catalytic converter can range from $500 to $2,500 depending on the vehicle.