Catalytic Converter: Testing and Inspection

THREE-WAY CATALYTIC CONVERTER (TWC) INSPECTION

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 TWC using O2S1 *1, O2S21 *2 PID for upstream HO2S and O2S12 *1, O2S22 *2 PID for downstream HO2S.

*1: Right bank
*2: Left bank

2. Monitor the appropriate PIDs.
3. Drive the vehicle for 10 min at 65 - 96 km/h {40 - 60 mph} to allow the front catalytic converter to reach operating temperature.
4. Stop the vehicle and leave it in a safe place.
5. Idle the engine.
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 (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 1.1 or more or there is no downstream HO2S inversion, the WU-TWC is functioning properly.
- If the ratio is less than 1.1 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)