Circuit Description

Heated Oxygen Sensor (HO2S) decreases amount of time required for system to enter closed-loop operation. ECM will diagnose 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 internal resistance is too high.

DTC will set also set when:

• Engine speed is greater than 40 RPM.
• Battery voltage between 7.5-15.0 volts.