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 MANUALSMAZDA1999626 ES, 2.5 D, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 194 (ENGINE CONTROL SYSTEM)HEATED OXYGEN SENSOR (HO2S) INSPECTIONHO2S HEATER RESISTANCE INSPECTION
1999 Mazda 626 ES, 2.5 D, Standard
HO2S Heater Resistance Inspection
1999 Mazda 626 ES, 2.5 D, StandardSECTION HO2S Heater Resistance Inspection
WARNING: This page is about a different car, the 2004 Mazda MPV. However, it is still accessible from the selected car via links, so may be relevant.
- Disconnect the HO2S (front or rear) connector.
- Measure the resistance between the following HO2S terminals.
- HO2S (Front, RH) and HO2S (Rear, RH)
- Terminal C and D
- HO2S (Front, LH) and HO2S (Rear, LH)
- Terminal C and D
- If not as specified, replace the HO2S.
- If the HO2S heater is okay, but PID value or any of PCM terminal 94, 93, 95, 96 voltage are out of specification, perform Circuit Open/Short Inspection .
Specification
Front (RH, LH): 5.0-6.8 ohms
Rear (RH, LH): 14.1-18.9 ohms
- HO2S (Front, RH) and HO2S (Rear, RH)
RENDER: 1.0x
NO RELATED
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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.