REAR HEATED OXYGEN SENSOR (HO2S) INSPECTION

Note

• Before performing the following inspection, make sure to follow the troubleshooting flowchart. (See Troubleshooting Procedure.)

Rear Heated Oxygen Sensor (HO2S) Voltage Inspection

1. Warm up the engine to normal operating temperature.

2. Disconnect the rear HO2S connector.

3. Connect the positive probe of the tester (digital type) to rear HO2S sensor terminal A, and the negative probe to rear HO2S sensor terminal B and measure the voltage.

4. Maintain the engine speed at 3,000 rpm until the voltage indicates approx. 0.5-0.7 V.

5. Verify that the voltage is as indicated in the table when the engine is raced repeatedly.

• If it cannot be verified, replace the rear HO2S. (See REAR HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION.)

Rear HO2S Voltage Inspection

Engine condition	Voltage (V)
Accelerated	0.5-1.0
Decelerated	0-0.5

Rear Heated Oxygen Sensor (HO2S) Heater Resistance Inspection

1. Disconnect the rear HO2S connector.

2. Measure the resistance between rear HO2S terminals C and D.

• If not within the specification, replace the rear HO2S. (See REAR HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION.)

Rear HO2S heater resistance

14.1-18.9 ohms [20 °C {68 °F}]

Circuit Open/Short Inspection

1. Disconnect the PCM connector.

2. Disconnect the rear HO2S connector.

3. Inspect the following wiring harnesses for open or short circuit. (Continuity inspection)

Open circuit

• If there is no continuity in the following wiring harnesses, there is an open circuit. Repair or replace the wiring harness.

– Rear HO2S terminal A and PCM terminal 2Q

– Rear HO2S terminal B and PCM terminal 1U

– Rear HO2S terminal C and main relay terminal C

– Rear HO2S terminal D and PCM terminal 2A

Short circuit

• If there is continuity in the following wiring harnesses, there is a short circuit. Repair or replace the wiring harness.

– Rear HO2S terminal A and body ground

– Rear HO2S terminal A and power supply

– Rear HO2S terminal B and body ground

– Rear HO2S terminal B and power supply

– Rear HO2S terminal D and body ground