Circuit Description

The DTC P0037 monitors the HO2S heater circuit current. The heater is powered through the ignition switch and is grounded through the ECM heater control. The ECM commands the heater ON by grounding the heater control circuit. The HO2S sensor must be at operating temperature in order to accurately measure the oxygen content of the exhaust gas. The heater allows the HO2S to reach operating temperature quickly.