Circuit Description

Heated Oxygen Sensor (HO2S) decreases amount of time required for system to enter closed-loop operation. ECM diagnoses the heater and its related circuit by continuously monitoring electrical current. ECM also monitors the internal resistance of the sensor. The measured value is compared to a reference internal resistance that is computed using the heater and exhaust gas temperature. DTC will set when oxygen sensor does not become active within 20 seconds after heater reaches 99°F (37°C).

DTC will set also set when:

• Engine is running
• Battery voltage not between 11.03-15.52 volts.
• 20 seconds has elapsed after heater reached closed-loop temperature.