DTC P0036: Ho2S Heater Circuit - Bank 1, Sensor 2: Description

WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The Heated Oxygen (HO2S) bank 1 sensor 2 is threaded into the front exhaust pipe directly behind the cylinder 1, 3, 5 pre-converter (cylinders 1, 3, 5 are closest to front of dash). The sensor is used by the ECM to determine the oxygen storage capability of the pre-converter, fuel trim biasing (time held lean or rich) and certain techniques used to diagnose DTCs associated with the pre-catalyst oxygen sensor. The sensor is equipped with a heater to provide additional heat to speed up sensor activation time. The ECM controls the heater by supplying a ground to Purple wire. The ECM will pulse the heater until it has determined exhaust pipe moisture has evaporated (engine run time between 0 and 200 seconds). After that, the ECM will command the heater on at a 100% duty cycle for 10 seconds, after which it will turn off the heater for a very short amount of time to test for an open/low voltage condition. The ECM will continue to do this unless the exhaust gas temperature exceeds 1562°F (850°C). The heater will be pulsed if this limit is exceeded. When the heater is commanded off (circuit not grounded), the voltage level at the ECM should be high (ignition voltage). When the heater is commanded on (circuit grounded), the voltage level at the ECM should be low. The ECM heater feedback circuit uses a pull-up voltage (2.6-4.6 volts), which allows the ECM to individually differentiate between an open, short to ground or short to voltage. DTC P0036 will set if the ECM detects an open heater control circuit when HO2S bank 1 sensor 2 is commanded off with the engine cranking/running.