P0422

THREE WAY CATALYTIC CONVERTER





Fault Symptom.
CHECK ENGINE lamp (MIL) on.

Conditions.
The voltage amplitude from the rear heated oxygen sensor is compared with the voltage amplitude from the front heated oxygen sensor and compared with a limit value.

Three way catalytic converter heating
Vehicle speed ~ 70 km/h for 3 minutes and 20 seconds.

Evaluation of the three way catalytic converter.
Gentle acceleration from idling speed up to 2000-2500 rpm and then varying engine load and speed between 2000 and 2500 rpm for a total time of 3 minutes and 20 seconds.

Diagnostic Help.
A temporary or permanent decrease in the capacity of the three way catalytic converter may be caused by:

^ Leaded fuel or fuel with a sulphur content.
^ Fuel additives.
^ Additives in the motor oil if oil consumption is abnormal.
^ High exhaust temperature.
^ Misfiring.
^ Misfiring caused by low fuel level/low fuel pressure.





Diagnostic Procedure.
1 Check the exhaust system

- Start the engine and run it at idling speed.
- Check the exhaust system for leakage between the engine and the rear heated oxygen sensor.

Any leakage?

YES:
^ Rectify the fault. Continue with point 3.
NO:
^ Change the catalytic converter. Continue with point 2.





2 Check the fuel system

- Check the fuel pressure and fuel pump delivery flow.

Are the readings OK?

YES:
^ Continue with point 3.
NO:
^ Rectify the fault. Continue with point 3.





3 Final check

- Clear the diagnostic trouble codes.