Possible Causes

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.