Possible Causes
WARNING: This page is about a different car, the 2002 Mazda B4000, 2002 Mazda B3000, and 2002 Mazda B2300. However, it is still accessible from the selected car via links, so may be relevant.
HO2S heater heats HO2S sensor to temperatures of 1400°F (760°C). VPWR circuit supplies voltage to heater with PCM completing circuit ground when proper conditions are present. Possible causes are:
- Shorts to VPWR in harness or HO2S.
- Water in connectors (contamination).
- Open VPWR circuit.
- Open ground circuit.
- Low battery voltage.
- Corrosion or poor mating materials and wiring.
- Damaged HO2S heater.
- Damaged PCM.