HO2S Bank 1 Sensor 1 and HO2S Bank 2 Sensor 1

The Heated Oxygen Sensor (HO2S) bank 1 sensor 1 (cylinders 1, 3, 5 which are closest to the front of dash) or Heated Oxygen Sensor (HO2S) bank 2 sensor 1 (cylinders 2, 4, 6 which are closest to the radiator) are both located in each exhaust manifold bank. Each sensor is used by the ECM to make fuel control corrections for each bank towards a 14.7 to 1 air/fuel ratio. The heated oxygen sensor 1 is an electrical source that responds to oxygen content in the exhaust manifold. When the sensor reaches approximately 316°C (600°F), it produces a voltage based on the difference in oxygen between the atmosphere and exhaust gas. At this temperature, the sensor is fully functional. The ECM sends a bias voltage (450 mV) on the signal line, which can be read on the Scan tool when the sensor is cold. When the heated oxygen sensor 1 is cold, it produces no voltage and has extremely high internal resistance. However, when the sensor heats up, it produces voltage that overrides the bias voltage. This voltage is read by the ECM to determine a rich/lean heated oxygen sensor 1 signal used to adjust injector pulse width. Under normal conditions, low sensor voltage means high oxygen content/lean air-fuel mixture and vice versa. Normal sensor readings will fluctuate between 60 mV and 1080 mV.

Each heated oxygen sensor 1 contains a heater element controlled by the ECM necessary to speed up closed loop start times. The ECM will pulse the heater until it has determined exhaust pipe moisture has evaporated (engine run time between 0 and 30 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 850°C (1562°F). The heater will be pulsed if this limit is exceeded.