The Heated Oxygen Sensor (HO2S) detects the presence of oxygen in the exhaust and produces a variable voltage according to the amount of oxygen detected. A high concentration of oxygen (lean air/fuel ratio) in the exhaust produces a voltage signal less than 0.4 volt. A low concentration of oxygen (rich air/fuel ratio) produces a voltage signal greater than 0.6 volt. The HO2S provides feedback to the PCM indicating air/fuel ratio in order to achieve a near stoichiometric air/fuel ratio of 14.7:1during closed loop engine operation. The HO2S generates a voltage between 0.0 and 1.1 volts.
Embedded with the sensing element is the HO2S heater. The heating element heats the sensor to a temperature of 800°C (1,472°F). At approximately 300°C (572°F) the engine can enter closed loop operation. The VPWR circuit supplies voltage to the heater. The PCM turns the heater on by providing the ground when the correct conditions occur. The heater allows the engine to enter closed loop operation sooner. The use of this heater requires the HO2S heater control to be duty cycled, to prevent damage to the heater.
Removal & Installation
With the vehicle in NEUTRAL, position it on a hoist.
NOTEIf necessary, lubricate the Heated Oxygen Sensor (HO2S) with lock lubricant to assist in removal.
- Using a suitable oxygen sensor removal tool, remove the HO2S.
- Apply a light coat of anti-seize lubricant to the threads of the HO2S.
- To install, reverse the removal procedure and tighten the sensor to 30 ft. lbs. (40 Nm).
- Scan and monitor HO2S signal pid.
- Check for clean and secure connections at harness.
- Check the internal resistance of the HO2S heater by disconnecting the sensor connector.
- Measure the resistance on the component side of the harness between (HO2S heater) Pin-1 and (VPWR) Pin-2
- The resistance should read between 3-30 ohms.
If the reading is not as specified suspect a faulty HO2S.