MX-5 Miata Mazdaspeed L4-1.8L DOHC Turbo (2004)
Catalytic Converter: Testing and Inspection
THREE-WAY CATALYTIC CONVERTER (TWC) INSPECTION
NOTE: Make sure that no HO2S DTC has been detected. If detected, this inspection cannot be used for TWC inspection.
1. Connect the WDS or equivalent and monitor PIDs as follows:
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Monitor TWO using O2S11 PID for upstream HO2S and O2S12 PID for downstream HO2S.
2. Begin monitoring the appropriate PIDs.
3. Drive the vehicle for 10 mm at 65 - 96 km/h (40 - 60 mph) to ensure the front catalytic converter reaches operating temperature.
4. Stop the vehicle and leave 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 (inversion) that the downstream HO2S graph line actually crosses the 0.5 V line.
NOTE: Do not count the number of peaks. Refer to the illustration.
10. Using the following equation, calculate the value of ratio.
Equation
RATIO = Upstream HO2S inversion + downstream HO2S inversion
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If the ratio is 2 or more or no downstream HO2S inversion, the TWC is functioning properly.
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If the ratio is less than 2, the TWC is not functioning properly. Replace the TWC
Upstream HO2S graph line example
