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.
2021 Mazda CX-3 AWDFACTORY OEM SERVICE PROCEDURE
PID/DATA Monitor Inspection (HO2S)
- Connect the M-MDS to the DLC-2.
- Start the engine and warm it up completely.
- Access the following PIDs using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST
.)
- VSS (Vehicle speed)
- RPM (Engine speed)
- O2S12 (HO2S output voltage)
- Drive the vehicle and decelerate the engine speed by releasing the accelerator pedal fully when the engine speed is 3, 000 RPM or more.
- Verify that the HO2S output voltage (PID: O2S12) changes as shown in the figure during deceleration. (outputs 0.6 V or more once or more, then 0.3 V or less.)
- If not as verified, replace the HO2S. (See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION .)
Factory Service Tools
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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.