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Home >> Mazda >> 2001 >> MPV DX V6-2.5L DOHC >> Repair and Diagnosis >> Powertrain Management >> Emission Control Systems >> Catalytic Converter >> Testing and Inspection
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Catalytic Converter: Testing and Inspection

Three-Way Catalytic Converter (TWC) Inspection

NOTE: Make sure that no HO2Ss DTC has been detected. If detected, this inspection cannot be used for TWC inspection.

1. Connect the NGS tester and monitor PIDs as following.
- Monitor the left WU-TWC using FHO2S L PID for upper stream HO2S and RHO2S L PID for lower stream HO2S.
- Monitor the right WU-TWC using FHO2S R PID for lower stream HO2S.
- Monitor TWC using MHO2S PID for upper stream HO2S and RHO2S PID for lower stream HO2S.

2. Press START to begin monitoring the appropriate PIDs.
3. Drive the vehicle for 10 minutes at 65 - 96 kph {40 - 60 mph} to ensure the front catalytic converter reaches operating temperature.
4. Stop the vehicle and leave in a safe place.
5. Let the engine at idle.
6. Press TRIGGER to begin recording PIDs.
7. Monitor appropriate PIDs and capture the PIDs DATA at least 3 minutes of HO2S activity then press TRIGGER again.
8. Select the appropriate PIDs and see the graph of "VIEW RECORDING".




9. Count the number of times (inversions) that the upper stream HO2S graph line actually crosses the 0.5 V line.
10. Count the number of times (inversion) that the lower stream HO2S graph line actually crosses the 0.5 V line.

NOTE: Do not count the number of peaks. See the illustration.

11. Using the following equation, calculate the value of ratio.

Equation
RATIO = upper stream HO2S inversion + lower stream HO2S inversion




Upper stream HO2S graph line




Lower stream HO2S graph line

- If the ratio is 2 or more or no lower stream HO2S inversion, the WU-TWC is functioning properly.
- If the ratio is less than 2, the WU-TWC is not functioning properly. Replace the WU-TWC.

Equation
3.7 (good converter) = 26 inversions (upper stream HO2S inversions) + 7 inversions (lower stream HO2S inversions)




Equation
0 (good converter) = 26 inversions (upper stream HO2S inversions) + 0 inversions (lower stream HO2S inversions)




Equation
1.4 (bad converter) =26 inversions (upper stream HO2S inversions) + 19 inversions (lower stream HO2S inversions)
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