Oxygen Sensor: Testing and Inspection

HEATED OXYGEN SENSOR (HO2S)

INSPECTION







FUNCTION AND OPERATION PRINCIPLE
Heated Oxygen Sensor (HO2S) consists of zirconium and alumina and is installed on upstream and downstream of the Manifold Catalyst Converter (MCC). After it compares oxygen consistency of the atmosphere with the exhaust gas, it transfers the oxygen consistency of the exhaust gas to the PCM. When AIF ratio is rich or lean, it generates approximately 1 V or 0 V respectively. In order that this sensor normally operates, the temperature of the sensor tip is higher than 370 degrees C (698 degrees F). So it has a heater which is controlled by the PCM duty signal. When the exhaust gas temperature is lower than the specified value, the heater warms the sensor tip.

Waveform:

Circuit Diagram:

COMPONENT INSPECTION
1. Check signal waveform of HO2S using a scantool.

Specification: Refer to "waveform".

2. Disconnect the HO2S connector.




3. Measure resistance between HO2S heater terminals 3 and 4.
4. Check that the resistance is within the specification.

Specification: Refer to SPECIFICATION.