Circuit Description

WARNING: This page is about a different variant/trim than selected.

Heating elements inside the heated oxygen sensor (HO2S) minimize the time required for the sensors to reach operating temperature and provide an accurate voltage signal. A low side driver within the engine control module (ECM) is pulse width controlled to provide current to the heater elements. The ECM will not allow continuous HO2S heating until calibrated limits of time, temperature, and intake airflow have been reached. The ECM continuously monitors the HO2S heater operating state by briefly turning OFF the heater low side driver at regular intervals. A small reference voltage of approximately 4.5 volts is present at the heater low control circuit. When the low side driver is commanded ON, the reference voltage is low, when the low side driver is commanded OFF the reference voltage is high, close to battery voltage. If the ECM detects that the HO2S heater low control circuit voltage is lower than 2.6 volts when the heater is commanded OFF, the following DTCs will set:

DTC P0031 for HO2S bank 1 sensor 1
DTC P0037 for HO2S bank 1 sensor 2
DTC P0051 for HO2S bank 2 sensor 1
DTC P0057 for HO2S bank 2 sensor 2