Three-Way Catalytic Converter (TWC) Inspection [L3]

WARNING: This page is about a different car, the 2005 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

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

Connect the WDS or equivalent and monitor PIDs as following.
- Monitor the TWC using O2S11^*1 , O2S12^*2 PID for upstream HO2S and O2S12^*1 , O2S13^*2 PID for downstream HO2S.
*1: Except for California emission regulation applicable ATX Model

*2: California emission regulation applicable ATX Model
Monitor the appropriate PIDs.
Drive the vehicle for 10 min at 65-96 km/h {40-60 mph} to allow the front catalytic converter to reach operating temperature.
Stop the vehicle and leave it in a safe place.
Idle the engine.
Record PIDs for 1 min .
Select the appropriate PIDs and read the graph.
Count the number of times (inversions) that the upstream HO2S graph line actually crosses the 0.5 V line.
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 Fig 1 .
Fig 1: Example Of HO2S Downstream Inversions
Courtesy of MAZDA MOTORS CORP.
Using the following equation, calculate the value of ratio.
Equation

RATIO = Upstream HO2S inversion divided by 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.