P0421

P0421

Diagnostic information - DME V8 DFI

Catalytic converter conversion, bank X

NOTE: Do not use contact spray on the oxygen sensor's plug connections as this will result in irreparable damage to the lines (blockage of reference air duct).

NOTE: Do not interchange the oxygen sensor ahead of catalytic converter with the sensor behind the catalytic converter as this will result in implausible fault entries.

Diagnostic conditions
- Perform following short tests in sequence :
1. All models: Oxygen sensor short tests
2. Short test Tank vent
3. Short test Fuel supply Partial load
4. Short test Fuel supply Idle speed
5. Short test Catalytic converter conversion

or:

- 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
- Lambda control ahead of catalytic converter active
- Lambda control behind catalytic converter ready for operation
- No detection of oxygen sensor, mass air flow sensor or throttle valve adjusting unit fault

Possible fault causes
- When registered lambda error: :
- nature of the problem
- Remedy oxygen-sensor fault according to instructions then
- after a brief test described above
- Leak in exhaust system between engine and oxygen sensor behind catalytic converter
--> this especially affects trips with a mass air flow of < 400 mg/stk
- Oxygen sensors ahead of and behind catalytic converter bank X are interchanged
- Catalytic converter bank X faulty