P0420
P0420TWC Conversion, Bank 1 - Above Limit
Diagnostic conditions
- Battery voltage between 10 V and 16 V
- Temperature at engine start-up greater than -15 °C
- Time after the engine is started longer than 10 seconds
- TWC temperature between 400 °C and 720 °C
- 60-second journey within load between 22 and 46 %
- EVAP canister burden less than 8
- Engine speed between 1,200 rpm and 2,600 rpm
- Oxygen sensing in front of catalytic converter active
- Oxygen sensing behind catalytic converter ready for operation
- No other mixture faults stored
Possible cause of fault
- Oxygen sensors in front of and behind catalytic converter are interchanged
- Catalytic converter faulty
Affected pins
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Diagnosis/troubleshooting
NOTE: Do not use contact spray on the oxygen sensor plug connections, as this may cause irreparable damage to the wiring (blocking the reference air channels).
NOTE: Do not confuse oxygen sensor ahead of catalytic converter and oxygen sensor behind catalytic converter as this will cause implausible fault entries.
Distinguishing feature of both sensors:
Oxygen sensor in front of catalytic converter (LSU) has a six pin plug
Oxygen sensor behind catalytic converter (LSF) has a four pin plug
NOTE: The diagnostic conditions can also be 'enforced' by the "TWC converting" short test using the 9588 Porsche System Tester II.
