Oxygen Sensor: Testing and Inspection

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HEATED OXYGEN SENSOR (HO2S)

INSPECTION

FUNCTION AND OPERATION PRINCIPLE

Heated Oxygen Sensor (HO2S) consists of zirconium and alumina and is installed 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 A/F 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 °C (698 °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.

SPECIFICATION
A/F Ratio Output Voltage (V)
RICH 0.80 - 0.92
LEAN 0.1

Item Specification
Heater Resistance (ohm) 3.0 - 4.0 ohms at 21 °C (69.8 °F)

Waveform:

WAVEFORM

Circuit Diagram:

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.