P0431 Catalytic Conversion

P0431

Catalytic conversion

NOTE: The catalytic converter monitor compares the amplitude of the oxygen sensor behind the catalytic converter with the amplitude of a computed limit catalytic converter during defined air gulping and enrichment phases. The amplitudes allow conclusions to be drawn about the ability of the catalytic converter to store oxygen.

Diagnostic conditions
- Engine start temperature > -15 °C (5 °F)
- Catalytic converter temperature 385 .... 635 °C (725-1175 °F)
- Loading of activated charcoal filter < 8
- Oxygen sensing in front of catalytic converter active
- Oxygen sensors behind catalytic converter ready for operation
- 50 seconds (cumulative) within following load/rpm range
- Engine speed 1280 .... 2880 rpm
- Engine load (relative filling) 22 .... 41%
- No fault oxygen sensors, tank vent, secondary-air pump relay, secondary-air valve relay, throttle adjusting unit, mass air flow sensor, no misfire.
- The diagnostic conditions can also be established using the PIWIS Tester via the short test "Catalytic conversion". It is not necessary to have the vehicle in motion for this.

Possible fault causes
- Oxygen sensors in front of and behind catalytic converter swapped (position in exhaust assembly)
- Valve lift error
- Aged oxygen sensor behind catalytic converter
- Catalytic converter faulty (pre-catalytic conversion rate too low)

If an aged oxygen sensor (oxygen sensor signal behind catalytic converter, dynamism) is detected together with this fault:
- remedy the fault "Oxygen sensor signal behind catalytic converter, dynamism" first,
- Then check if this fault - catalytic conversion - has been entered again.

IMPORTANT: If the primary catalytic converter is faulty, check the main catalytic converter for damage and also replace it if necessary.