Possible causes – Faulty Heated Oxygen Sensor Bank 1 or 2– Heated Oxygen Sensor Bank 1 or 2 harness is open or shorted– Heated Oxygen Sensor Bank 1 or 2 circuit poor electrical connection Symptoms – Engine Light ON (or Service Engine Soon Warning Light) P1031 PONTIAC OBD Code Description Heated Oxygen Sensor (HO2S)