P0491

P0491

Diagnosis information - DME

Secondary-air system

NOTE:
- The secondary diagnosis is not carried out during secondary air injection after cold start, but at a later point in time ("intrusive check").
- In this process, the secondary air pump is activated and the excess air is determined via the oxygen sensor.

The secondary air diagnostics can be activated via the short test menu on the PIWIS Tester.

Diagnostic conditions
- Secondary air system diagnosis is not yet performed in this cycle
- Correction factor, height > 0.73
- Intake air temperature 5 °C ... 60 ° C
- Engine starting temperature < 42 °C
- Engine temperature 5 °C ... 102 ° C
- Exhaust temperature < 650 °C
- Mass air flow 13 kg/h... 50 kg/h
- Oxygen sensors in front of catalytic converter ready for operation
- Idle speed
- Time after engine starts > 590 s
- No relevant faults stored

Possible fault causes
- Secondary air pump relay mechanically faulty (lams)
- Power supply for secondary air pump faulty
- Air duct cross section narrowed (pinched / blocked)
- Electric switch-over valve does not function
- Pneumatic switch-over valve does not function
- Leak in vacuum system
- Secondary air pump electrically or mechanically faulty