DTC 4-4-3

4-4-3 THREE-WAY CONVERTER EFFICIENCY

Preconditions for DTC
^ The ECM continuously monitors the Three-Way Converter's (TWC) efficiency by comparing the signal from the rear Heated Oxygen Sensor (HO2S) with the signal from the front Heated Oxygen Sensor (HO2S). When the TWC's efficiency deviates too much, the ECM sets DTC 4-4-3.

Substitute value
^ None.

Fault sources
^ Uneven compression.
^ Air leakage in the intake system.
^ Air leakage in the exhaust system.
^ Incorrect fuel pressure.
^ Defective TWC.

Fault symptoms
^ May result in poorer performance.

TESTING PROCEDURE





Other DTCs
^ Read off the other DTCs.

If any DTC for misfiring is stored:
- See: Testing By Trouble Code, DTC 5-4-3 Misfire at Least 1 Cylinder.
If DTC 4-3-5 is stored:
- See: Testing By Trouble Code, DTC 4-3-5 Front Heated Oxygen Sensor Slow Response.
If DTC 4-3-6 is stored:
- See: Testing By Trouble Code, DTC 4-3-6 Rear Heated Oxygen Sensor Compensation.
If none of the above DTC's are stored:
- Check the engine compression.





Checking the Compression
^ Carry out a compression test.

If the compression is OK:
- Check for air leakage in the intake system.
If the compression in any cylinder deviates:
- Rectify as necessary.





Checking for Air Leakage in the Intake System
^ Check if there is any air leakage.

If there is no air leakage:
- Check for air leakage in the exhaust system.
If there is air leakage:
- Rectify as necessary.





Checking for Air Leakage in the Exhaust System
^ Check if there is any air leakage.

If there is no air leakage:
- Check the fuel and residual pressure.
If there is air leakage:
- Rectify as necessary.





Checking Fuel and Residual Pressure
^ Check fuel and residual pressure.

If fuel and residual pressure are OK:
- Test with a new TWC.
If the fuel or residual pressure are incorrect:
- Rectify as necessary.