Catalytic Converter: Testing and Inspection

WARM-UP THREE-WAY CATALYTIC CONVERTER (WU-TWC) INSPECTION

NOTE: Make sure that no HO2S DTCs has been detected. If detected, this inspection is not applicable for TWC inspection.

1. Connect the WDS or equivalent and monitor PIDs as following.
- Monitor the left WU-TWC using O2S21 PID for upstream HO2S and O2S22 PID for downstream HO2S.
- Monitor the right WU-TWC using O2S11 PID for upstream HO2S and O2S12 PID for downstream HO2S.

2. Begin to monitor the appropriate PIDs.
3. Drive the vehicle for 10 min at 65 - 96 km/h (40 - 60 mph} to ensure the front catalytic converter reaches operating temperature.
4. Stop the vehicle and leave it in a safe place.
5. Let the engine at idle.
6. Record PIDs for 1 min.




7. Select the appropriate PIDs and read the graph.
8. Count the number of times (inversions) that the upstream HO2S graph line actually crosses the 0.5 V line.
9. Count the number of times (inversion) that the downstream HO2S graph line actually crosses the 0.5 V line.

NOTE: Do not count the number of peaks. Refer to the illustration.

10. Using the following equation, calculate the value of ratio.

Equation:
RATIO Upstream HO2S inversion downstream HO2S inversion

- If the ratio is 2 or more or there is no downstream HO2S inversion, the WU-TWC is functioning properly.
- If the ratio is less than 2, the WU-TWC is not functioning properly. Replace the WU-TWC.




Upstream HO2S graph line example




Downstream HO2S graph line example 1

Equation
RATIO = 26 inversions (upstream HO2S inversions) / 7 inversions (downstream HO2S inversions) = 3.7 (good WU-TWC)




Downstream HO2S graph line example 2




Downstream HO2S graph line example 3

Equation
RATIO = 26 inversions (upstream HO2S inversions) / 1.9 Inversions (downstream HO2S inversions) = 1.4 (deteriorated - WU-TWC)