Catalytic Converter: Testing and Inspection
THREE-WAY CATALYTIC CONVERTER (TWC) INSPECTIONNOTE: Make sure that no HO2S DTCs have been detected. If detected, this inspection is not applicable for TWC inspection.
1. Connect the WDS or equivalent and monitor the following PIDs.
- Monitor the right TWC using 02S11 PID for upstream HO2S and 02S12 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 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 the 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
Upstream HO2S graph line example:
Downstream HO2S graph line example 1:
Downstream HO2S graph line example 2:
Downstream HO2S graph line example 3:
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 TWC is functioning properly
- If the ratio is less than 1.5, the TWC is not functioning properly Replace the TWC.
Equation
RATIO = 30 inversions (upstream HO2S inversions) + 5 inversions (downstream HO2S inversions) = 6.0 (good WU-TWC)
Equation
RATIO = 30 inversions (upstream HO2S inversions) + 27 inversions (downstream HO2S inversions) =1.1 (bad converter)