Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSMAZDA20086 S SPORT, 4D HATCHBACK, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 62 (ENGINE CONTROLS [SYSTEM & COMPONENT TESTING])EMISSION SYSTEMS & SUB-SYSTEMSWARM UP THREE-WAY CATALYTIC CONVERTERINSPECTION

2008 Mazda 6 s Sport, 4D Hatchback, Standard

Warm Up Three-Way Catalytic Converter: Inspection

2008 Mazda 6 s Sport, 4D Hatchback, StandardSECTION Inspection

WARNING: This page is about a different car, the 2003 Mazda Protege5, 2003 Mazda Protege, 2003 Mazda MX-5 Miata, 2003 Mazda MPV, and 2003 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Ensure no HO2S DTC has been detected. If detected, this inspection cannot be used.

Using scan tool, access O2S11 (front HO2S) and O2S12 (rear HO2S) PIDs.
Monitor appropriate PIDs.
Drive vehicle for 10 minutes at 40-60 MPH to ensure Warm Up Three-Way Catalytic Converter (WU-TWC) reaches operating temperature.
Stop vehicle, let engine idle and record PIDs for one minute.
Select appropriate PIDs and read graph. See Fig 1 or Fig 2 .
Count number of times graphline actually crosses .5V line (inversion) for both front and rear HO2Ss.
Divide number of front HO2S inversions by number of rear HO2S inversions for ratio data.
- If ratio is 2 (1.5 on Mazda6) or more or no rear HO2S inversions, WU-TWC converter is functioning properly.
- If ratio is less than 2 (1.5 on Mazda6), WU-TWC converter has deteriorated. See Fig 3. Replace faulty WU-TWC converter.

Fig 1: Identifying Front HO2S Graphline - Example

Courtesy of MAZDA MOTORS CORP.

RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.