Diagnostic Aids

Malfunction code will set if, no signal when ignition switch is turned on. Signal below lower limit when ignition switch is turned on, or signal above upper limit when ignition switch is turned on. Check for following possible problems:

• Open or short between rear Heated Oxygen Sensor (HO2S) and Main or Fuel Pump relay.
• Open or short between rear HO2S and ECM.
• Incorrect rear HO2S heater resistance.
• Faulty rear HO2S.