Circuit Description

Heated Oxygen Sensor (HO2S) bank, 1 sensor 1, monitors oxygen content in exhaust gasses before they enter into catalytic converter. ECM monitors this voltage and determines if exhaust is lean or rich and increases or decreases the injector pulse width.

DTC will set when signal from front HO2S conflicts with reading from rear oxygen sensor, and will default system into closed loop. DTC will also set when:

• Front oxygen sensor value is between 0.95-1.005 and rear oxygen sensor reads greater than 650 millivolts (rich) or less than 300 millivolts (lean).
• Front oxygen sensor value is greater than 1.2 (lean) and rear sensor is indicating rich.
• Front oxygen sensor value is less than 0.8 (rich) and rear sensor is indicating lean.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. ECM will record operating conditions at time of failure and store information in freeze frame buffer.