40 - TWC Conversion, Bank 1 Above Limit
P0420 - TWC CONVERSION, BANK 1 ABOVE LIMIT
Diagnosis conditions
- TWC temperature 420 - 600 °C
- 85 seconds within rpm/load range (cumulative)
- EVAP canister burden < 8
- Speed 1280-2440 rpm
- 20 - 40% engine load (relative air charge)
- Oxygen sensing ahead of TWC is active
- Oxygen sensing after TWC ready for operation
- Engine starting temperature > -20 °C
- No faults in memory
Possible fault cause
- Oxygen sensor ahead of and after TWC exchanged
- Valve lift fault
- Aged oxygen sensor after TWC
- TWC faulty
Diagnosis/Troubleshooting
NOTE: If an aging oxygen sensor is recorded in conjunction with a fault in the TWC, a check must be performed with a new oxygen sensor to see whether a TWC fault is still indicated.
