DTC P0135: Ho2S1 Heater Performance: Description

The Heated Oxygen Sensor 1 (HO2S1) is an electrical source that responds to oxygen content in the exhaust manifold. When the sensor reaches approximately 600°F (316°C), it produces a voltage based on the difference in oxygen between the atmosphere and exhaust gas. When the HO2S1 is cold, it produces no voltage and has extremely high internal resistance. The internal resistance of the sensor is much greater than the resistance of the bias pull-up resistor. A heater element is required to provide additional heat which accelerates sensor activation time. The heater is supplied ignition is turned On and the PCM provides a ground when the conditions necessary to perform the test are met. The PCM will monitor the heater current to determine if the heater is working properly. DTC P0135 sets when the HO2S1 heater current is not within the calibrated range.