P0421 Diagnosis Information - DME (DFI)

P0421

Diagnosis Information - DME (DFI)

Catalytic converter, bank 1, inadequate effect

Diagnostic conditions
- Engine temperature > 60 °C (140 °F)
- Time after engine starts > 10 seconds
- Catalytic converter temperature 500 °C ... 800 °C (932 °F ... 1,472 °F)
- 60 second drive with gentle acceleration at 25 ... 130 km/h (16...81 mph)
- Loading of carbon canister < 0.4
- Engine speed < 3,000 rpm
- Secondary air not active
- Tank ventilation not active
- Oxygen sensing ahead of catalytic converter active
- Oxygen sensing behind catalytic converter ready for operation
- No detection of oxygen sensor, mass air flow sensor or throttle valve adjusting unit fault

Possible fault causes
- Leak in exhaust system between engine and oxygen sensor behind catalytic converter
this is particularly relevant when driving with a mass air flow > 400 mg/stk
- Oxygen sensors ahead of and behind catalytic converter bank 1 are interchanged
- Catalytic converter bank 1 faulty