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.

2004 Mazda MX-5 Miata Base, AutomaticFACTORY OEM SERVICE PROCEDURE

Open Circuit

If there is no continuity, the circuit is open. Repair or replace the harness.
- Heated oxygen circuit (HO2S connector terminal A and PCM connector terminal 4W (Front)).
- GND circuit (HO2S connector terminal B and PCM connector terminal 4O through common connector (Front)).
- Heated oxygen circuit (HO2S connector terminal A and PCM connector terminal 4AA (Rear)).
- GND circuit (HO2S connector terminal B and PCM connector terminal 4O through common connector (Rear)).
Fig 1: Identifying Front & Rear Heated Oxygen Sensor [BP, BP With TC] Harness Side Connector Terminals
Courtesy of MAZDA MOTORS CORP.

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.