Oxygen Sensor: Testing and Inspection

HEATED OXYGEN SENSOR (HO2S) INSPECTION[AJ]

NOTE: Before performing the following inspection, make sure to follow the troubleshooting flowchart. (See FOREWORD[AJ].)

HO2S voltage inspection
1. Warm up the engine to normal operating temperature.
2. Using the M-MDS, monitor the following:
- Vehicle speed (PID: VSS)
- Engine speed (PID: RPM)
- HO2S voltage (PID: 02S11/02S12/02S21/02S22)

3. Drive the vehicle and decelerate the engine speed by releasing the accelerator pedal fully when the engine speed is 3,000 rpm or more.




4. Verify that the HO2S outputs a voltage of 0.6 V or more, one time or more, then verify that the HO2S voltage (PID: 02S1 l/02S12/02S21/02S22) is 0.3 V or less while decelerating as shown in the figure.
- If not within the specification, inspect the HO2S for an open or short circuit. (See HO2S circuit open/short inspection (sensor).) Then if there is no malfunction in the wiring harness, replace the HO2S.




HO2S circuit open/short inspection (sensor)
1. Disconnect the PCM connector.
2. Disconnect the H028 connector.
3. Inspect the following wiring harnesses for an open or short circuit. (Continuity inspection)

Open circuit
- It there is no continuity, there is an open circuit. Repair or replace the wiring harness.
- HO2S (RF) terminal A and PCM terminal 2AK
- HO2S (RF) terminal B and PCM terminal 2AV
- HO2S (LF) terminal A and PCM terminal 2AL
- HO2S (LF) terminal B and PCM terminal 2AX
- HO2S (RR) terminal A and PCM terminal 2AG
- HO2S (RR) terminal B and PCM terminal 2AY
- HO2S (LR) terminal A and PCM terminal 2AH
- HO2S (LR) terminal B and PCM terminal 2BA

Short circuit
- If there is continuity, there is a short circuit. Repair or replace the wiring harness.
- HO2S (RF) terminal A and power supply
- HO2S (RF) terminal A and body ground
- HO2S (RF) terminal B and power supply
- HO2S (LF) terminal A and power supply
- HO2S (LF) terminal A and body ground
- HO2S (LF) terminal B and power supply
- HO2S (RR) terminal A and power supply
- HO2S (RR) terminal A and body ground
- HO2S (RR) terminal B and power supply
- HO2S (LR) terminal A and power supply
- HO2S (LR) terminal A and body ground
- HO2S (LR) terminal B and power supply

HO2S heater resistance inspection
1. Disconnect the HO2S connector.




2. Measure the HO2S resistance between terminals C and D.
- It not within the specification, replace the HO2S.

HO2S heater resistance
HO2S (RF, LF) heater: 2-50 ohms
HO2S (RR, LR) heater: 2-50 ohms




HO2S circuit open/short inspection (heater)
1. Disconnect the PCM connector
2. Disconnect the HO2S connector.
3. Inspect the following wiring harnesses for an open or short circuit. (Continuity inspection)

Open circuit
- If there is no continuity, there is an open circuit. Repair or replace the wiring harness.
- HO2S (RF) terminal C and ignition switch
- H025 (RF) terminal D and PCM terminal 2AW
- HO2S (LF) terminal C and ignition switch
- HO2S (LF) terminal D and PCM terminal 2AS
- HO2S (RR) terminal C and ignition switch
- HO2S (RR) terminal D and PCM terminal 2AT
- H025 (LR) terminal C and ignition switch
- HO2S (LR) terminal D and PCM terminal 2A0

Short circuit
- If there is no continuity, there is a short circuit. Repair or replace the wiring harness. HO2S (RF) terminal C and body ground
- HO2S (RF) terminal D and power supply
- HO2S (RF) terminal D and body ground
- HO2S (LF) terminal C and body ground
- HO2S (LF) terminal D and power supply
- H025 (LF) terminal D and body ground
- HO2S (RR) terminal C and body ground
- H025 (RR) terminal D and power supply
- HO2S (RR) terminal D and body ground
- HO2S (LR) terminal C and body ground
- HO2S (LR) terminal D and power supply
- HO2S (LR) terminal D and body ground