A Heated Oxygen Sensor (HO2S) is mounted on the muffler inlet pipe, just below the three-way catalytic converter. The sensor monitors the oxygen content in the three-way catalytic converter and then transmits this information to the Powertrain Control Module (PCM). The PCM then adjusts the air/fuel ratio to provide a rich (more fuel) or lean (less fuel) condition.
See Figures 1 and 2
Perform a visual inspection of the heated oxygen sensor as follows:
- Disconnect the electrical lead, then remove the sensor from the exhaust system.
- If the sensor tip has a black/sooty deposit, this may indicate a rich fuel mixture.
- If the sensor tip has a white, gritty deposit, this may indicate an internal coolant leak.
- If the sensor tip has a brown deposit, this could indicate oil consumption.
All these contaminants can destroy the sensor; if the problem is not repaired, the new sensor will also be damaged.
- Reinstall the heated oxygen sensor, but do not connect its electrical lead.
- Measure resistance between the PWR and GND (heater) terminals of the sensor. If the reading is about 6 ohms at 68°F (20°C) the sensor's heater element is okay. Connect the sensors electrical lead.
- With the heated oxygen sensor connected and the engine running, measure voltage with a DVOM by backprobing the SIG RTN wire of the HO2S connector. The voltage readings at idle should stay below 1.0 volts. When the speed is increased or decreased, the voltage should fluctuate between 0 and 1.0 volts; if so, the sensor is okay.
REMOVAL & INSTALLATION
See Figures 3, 4 and 5
- Disconnect the negative battery cable.
- Raise the car and support it with safety stands.
- Unplug the Heated Oxygen Sensor (HO2S) electrical connection.
- Disengage the wiring from the retaining clips.
- Use oxygen sensor wrench T94P-9472-A, or equivalent open end wrench, to remove the sensor.
- Apply anti-seize compound to the oxygen sensor threads.
- Use oxygen sensor wrench T94P-9472-A or equivalent to install the sensor.
- Engage the sensor electrical connection and the wiring to the clips.
- Lower the car and connect the negative battery cable.