P0420

P0420
TWC Conversion Too Low (cylinders 1 - 3).

P0430
TWC Conversion Too Low (cylinders 4 - 6).

Function:
In order to assess the conversion efficiency of the catalytic converter, the oxygen absorption efficiency of the converter is established through comparison of the oxygen sensor amplitudes before and after the TWC. The conversion efficiency of the catalytic converter is reduced if the oxygen absorption efficiency is reduced due to converter aging.

Diagnostic Procedure:
- Catalytic converter temperature > 368°C.
- 4 speed/load ranges must be attained for at least 300 seconds.
- No Throttle position sensor fault.
- Oxygen sensing is active before catalytic converter.
- Oxygen sensors behind catalytic converter are ready for operation.
- No excessive load of the evaporative emission (EVAP) canister.
- No oxygen sensor heating fault.
- No oxygen sensor aging fault.
- No misfire detection fault.
- No adaptation fault limits exceeded.
- No mass air flow sensor fault.
- No fault in the fuel tank ventilation system or in the fuel tank ventilation end stage.
- The speed must be in the range between 1080 rpm and 3000 rpm.
- The engine load must be between 0.7 ms and 2.8 ms.

The oxygen absorption efficiency of the catalytic converter is established in 4 speed/load ranges. A fault is detected if the limit values are exceeded in 3 ranges.

NOTE: If an aged oxygen sensor is signalled together with a catalytic converter fault, perform a test with a new oxygen sensor in order to determine whether the catalytic converter fault will still be signalled.

Diagnostic Procedure: