Circuit Description

Powertrain Control Module (PCM) supplies about .45 volt to Heated Oxygen Sensor 1 (HO2S 1). The HO2S 1 generates a voltage that varies from about one volt when exhaust is rich to about .10 volt when exhaust is lean. PCM monitors and stores sensor voltage information and evaluates the voltage samples to determine amount of time sensor voltage is out of range. If PCM detects HO2S 1 voltage remains at or near .45 volt for an extended period of time, DTC will set.

Conditions for setting this DTC are as follows:

• No active misfire, fuel injector circuit, TP sensor, EVAP, IAT sensor, MAP sensor, fuel trim, EGR, ECT sensor, MAF sensor or CKP sensor DTCs set.
• Engine has been running for greater than 30 seconds.
• HO2S 1 signal voltage remains 400-500 mV for greater than 10 seconds.
• Engine coolant temperature is greater than 149°F (65°C).