Catalytic Converter: Testing and Inspection

WARM-UP THREE-WAY CATALYTIC CONVERTER (WU-TWC) INSPECTION [L3]

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

1. Connect the WDS or equivalent and monitor PIDs as following.
- Monitor the WU-TWC using 02S11 PID for upstream HO2S and 02S12 PID for downstream HO2S.

2. Monitor the appropriate PIDs.
3. Drive the vehicle for 10 minutes at 65-96 km/h (40-60 mph) to allow the front catalytic converter to reach operating temperature.
4. Sop the vehicle and leave it in a safe place.
5. Idle the engine.
6. Record PIDs for 1 minutes.
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 (inversions) that the downstream HO2S graph line actually crosses the 0.5 V line.

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

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

Equation: RATIO = Upstream HO2S inversion - downstream HO2S inversion

- If the ratio is 1.5 or more or there is no downstream HO2S inversion, the WU-TWC is functioning properly.
- If the ratio is less than 1.5, the WU-TWC is not functioning properly. Replace the WU-TWC.




Upstream HO2S graph line example




Downstream HO2S graph line example 1

Equation: RATIO = 30 inversions (upstream HO2S inversions) - 5 inversions (downstream HO2S inversions) = 6.0 (good WU-TWC)




Downstream HO2S graph line example 2




Downstream HO2S graph line example 3

Equation: RATIO = 30 inversions (upstream HO2S inversions) - 27 inversions (downstream HO2S inversions) = 1.1 (bad WU-TWC)