FRONT HEATED OXYGEN SENSOR (HO2S) INSPECTION [LF, L3]

Note

• Before performing the following inspection, make sure to follow the procedure as indicated in the troubleshooting flowchart.

Front HO2S Voltage Inspection

1. Warm up the engine to normal operating temperature.

2. Disconnect the front HO2S connector.

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

4. Run the engine 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 front HO2S.

Front HO2S voltage

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

Circuit Open/Short Inspection (Sensor)

1. Disconnect the PCM connector. (See PCM REMOVAL/INSTALLATION [LF, L3].)

2. Inspect the following wiring harnesses for open or short. (Continuity check)

Open circuit

• If there is no continuity, the circuit is open. Repair or replace the harness.

- HO2S terminal A and PCM terminal 2AG

- HO2S terminal B and PCM terminal 2AA

Short circuit

• If there is continuity, the circuit is shorted. Repair or replace the harness.

- HO2S terminal A and body GND

- HO2S terminal A and power supply

- HO2S terminal B and power supply

Front HO2S Heater Resistance Inspection

1. Disconnect the front HO2S connector.

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

• If not within the specification, replace the front HO2S.

Front HO2S heater resistance

2.16- 2.90 ohms [20 °C {68 °F}]

Circuit Open/Short Inspection (Heater)

1. Disconnect the PCM connector. (See PCM REMOVAL/INSTALLATION [LF, L3].)

2. Inspect the following wiring harnesses for open or short. (Continuity check)

Open circuit

• If there is no continuity, the circuit is open. Repair or replace the harness.

- HO2S terminal C and main relay terminal E

- HO2S terminal D and PCM terminal 2G

Short circuit

• If there is no continuity, the circuit is shorted. Repair or replace the harness.

- HO2S terminal C and body GND

- HO2S terminal D and power supply

- HO2S terminal D and body GND