Trouble Code Conditions

4-4-3 THREE-WAY CATALYTIC CONVERTER EFFICIENCY





Trouble Code Conditions
- The engine control module (ECM) continuously monitors three-way catalytic converter (TWC) efficiency by comparing the signal from the rear heated oxygen sensor (HO2S) with the signal from the front heated oxygen sensor. When three-way catalytic converter efficiency deviates too much the engine control module stores diagnostic trouble code (DTC) EFI-443.

Substitute value(s)
- None.

Possible source(s)
- Uneven compression.
- Air leakage in the intake system.
- Air leakage in the exhaust system.
- Faulty fuel pressure.
- Defective three-way catalytic converter.

Fault symptom(s)
- May result in poor performance.





Other Diagnostic Trouble Codes
- Read off other diagnostic trouble codes (DTCs).

If any misfire-related diagnostic trouble code is stored:
^ Select Alternative 1.

If diagnostic trouble code EFI-435 is stored:
^ Select Alternative 2.

If diagnostic trouble code EFI-436 is stored:
^ Select Alternative 3.

If none of the above diagnostic trouble codes have been stored:
^ Select Alternative 4.

Select an Alternative.
- Select one of the following options to continue.

Alternative 1:
^ Code EFI-45X, EFI-543, EFI-545, EFI-55X Misfire Cylinder X.

Alternative 2:
^ Code EFI-435 Front Heated Oxygen Sensor Too Slow.

Alternative 3:
^ Code EFI-436 Rear Heated Oxygen Sensor Compensation.

Alternative 4:
^ Proceed to Status Messages section below.





Status Message
- Proceed to Faulty Signal: