Main Catalyst Efficiency Below Threshold (Bank 1)
P0422 indicates the catalyst monitor reports that main-catalyst efficiency on Bank 1 is below the calibrated threshold. Learn what to inspect before replacing parts.
What you may notice
Symptoms
- 01Warning light may illuminate
- 02Intermittent or implausible live data
- 03Symptoms vary by vehicle
Where to look first
Common causes
- 01An aged or contaminated catalyst may be involved, but exhaust leaks, oxygen-sensor faults, misfires, or fuel-control problems can also affect the monitor.
- 02Wiring or connector fault
- 03Vehicle-specific operating condition
A sensible sequence
Best diagnostic order
- 01Save codes and freeze-frame information
- 02Check for exhaust leaks and related fuel-trim, misfire, and oxygen-sensor codes before condemning the converter.
- 03Compare live data with vehicle specifications
- 04Confirm the repair under the conditions that set the code
Step by step
What to check and repair
- 01Check for exhaust leaks and related fuel-trim, misfire, and oxygen-sensor codes before condemning the converter.
- 02Repair the confirmed cause and verify the result
Read the signals
Live-data clues
Affected sensor or switch input
- Typical behavior
- Plausible and consistent with operating conditions
- Possible clue
- A fixed or intermittent value can help localize the circuit fault
| Parameter | Typical behavior | What it can suggest |
|---|---|---|
| Affected sensor or switch input | Plausible and consistent with operating conditions | A fixed or intermittent value can help localize the circuit fault |
What P0422 means
The catalyst monitor reports that main-catalyst efficiency on Bank 1 is below the calibrated threshold. This code describes an observed condition and does not prove that the sensor itself has failed.
Diagnostic direction
Check for exhaust leaks and related fuel-trim, misfire, and oxygen-sensor codes before condemning the converter.
Before clearing the code
Save stored and pending codes and freeze-frame data. Use the procedure for the exact vehicle, repair the verified cause, and confirm the fault does not return.