Catalytic Converter: Testing and Inspection

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

California Emission Regulation Applicable Models

CAUTION: Perform the following procedures, DTC P0421 is indicated only.

1. Connect the WDS or equivalent to the DLC-2.
2. Start the engine and warm it up to normal operating temperature.
3. Turn off the engine.
4. Verify that the engine compression is within the specification. (See COMPRESSION INSPECTION.)
- If the compression pressure is not within the specification, repair or replace the malfunction part.

5. Drive the vehicle for 10 min at 65 - 96 km/h {40 - 60 mph} to allow the front catalytic converter to reach operating temperature.
6. Stop the vehicle and leave it in a safe space.
7. Access Test ID 10:21:80 on the "Diagnostic Monitoring Test Result" function.
8. Verify that the test result is within the specified indicated on the WDS or equivalent.
- If it is not as specified, replace the front catalytic converter.

Except for California Emission Regulation Applicable Models

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 O2S11 PID for upstream HO2S and O2S12 PID for downstream HO2S.

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 1.5 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)