P0421

P0421

Diagnosis information - Control unit DME (DFI)

Primary catalytic converter Bank 1 - Effect too low

INFORMATION
- Do not interchange the oxygen sensor in front of the 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 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 (°F)
- Period since engine was started > 10 Second(s)
- Catalytic converter temperature 470 ... 800 °C (°F)
- 60 Second(s) Driving with slight acceleration at 25 ... 130 km/h
- loading Charcoal canister < 0.7
- Engine speed < 3,000 1/min
- Secondary air injection not active (only EU5)
- Lambda control Ahead of catalytic converter Active
- Lambda control Behind catalytic converter Active
- none of the following faults stored : Oxygen sensor(s) - Electrical fault , Intake manifold pressure sensor or Throttle adjusting unit

Possible fault causes
- If an oxygen sensor fault is entered:
- corresponding fault cause
-->Remedy oxygen-sensor fault according to instructions
-->then perform short test as described above

- Exhaust system leaks between Engine and Oxygen sensor behind catalytic converter
-->above all at Mass air flow < 400 mg/stroke
- Oxygen sensor in front of catalytic converter and Behind catalytic converter Bank 1 interchanged
- Catalytic converter Bank 1 Faulty