Main Catalyst Efficiency Below Threshold (Bank 2)
Generic main catalyst efficiency code on bank 2 — used by some manufacturers in addition to or instead of P0420. Indicates the same root cause — degraded oxygen storage in the main catalyst.
Affected components
- Catalytic converter
- Oxygen sensor upstream
- Oxygen sensor downstream
Common causes
- High likelihood: Catalyst aged or contaminated
- Medium likelihood: Oxygen sensor drift
Possible symptoms
- Check engine light on
- Failed emissions inspection
- Possibly slightly increased fuel consumption
- Sulfur (rotten egg) smell from exhaust under load
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
Related codes
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.