DTC P0135: Ho2S Heater Circuit Performance - Bank 1, Sensor 1: Description

Heated Oxygen Sensor Bank 1 Sensor 1 (HO2S11) is equipped with a heater element to decrease amount of time required to enter closed loop fuel control. Engine Control Module (ECM) controls heater by pulsing heater ground circuit. When heater is commanded off (not grounded), voltage level at ECM should be high (ignition voltage). When heater is commanded on (grounded), voltage level at ECM should be low. ECM heater feedback circuit uses a pull-up voltage (1.6-3.6 volts), which allows ECM to individually differentiate between an open, short to ground or short to voltage. DTC sets when ECM detects HO2S11 does not become active within a certain length of time of exhaust temperature reaching 1112°F (600°C).