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 downstream of the converter detect that the converter is not reducing exhaust emissions as effectively as required. This can be caused by a failing catalytic converter, exhaust leaks, or issues with the oxygen sensors themselves. If left unaddressed, it may lead to increased emissions and potential damage to other components.
1. Most Common Causes
- Failed or inefficient catalytic converter (internal monolith damage)
- Faulty or contaminated downstream oxygen (O2) sensor
- Degraded or slow-responding upstream oxygen (O2) sensor
- Exhaust leak near the catalytic converter or O2 sensors
- O2 sensor wiring shorted, open, or with high resistance
- Faulty powertrain control module (PCM) - rare
- Poor fuel quality or silicon/lead contamination of the catalytic converter
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Failed emissions test
- Decreased fuel economy
- Possible rotten egg smell from exhaust
3. Step-by-Step Diagnosis
Step 1: Scan for codes and verify P0422 is present.
Step 2: Inspect exhaust system for leaks or damage.
Step 3: Monitor oxygen sensor data with a scan tool to compare upstream and downstream readings.
Step 4: Perform a catalytic converter efficiency test if necessary.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, but it may cause further damage to the catalytic converter and other components over time. It is best to diagnose and repair promptly.
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.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.