1995 Mazda B3000 Base, StandardFACTORY OEM SERVICE PROCEDURE

Heated Oxygen Sensor (Ho2S)

NOTE: HO2S is located in exhaust pipe, upstream of the catalytic converter. Faults in sensor or circuit should set a service code. See appropriate TESTS W/CODES article.
  1. To test sensor, warm engine to operating temperature. Unplug sensor. Connect DVOM positive lead to Gray/Light Blue wire (Red/Light Green on some sensors) on HO2S. Connect DVOM negative lead to Orange wire on HO2S.
  2. Start engine and run at high and low speeds while monitoring voltage. Voltage should fluctuate between 0.2-1.0 volt. If voltage is not as specified, replace sensor.
  3. To check sensor heater, measure resistance between remaining 2 terminals. With sensor at room temperature, resistance should be 2-5 ohms. With sensor warm to hot, resistance should be 5-30 ohms. If resistance is not as specified, replace sensor.
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.

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