Oxygen Sensor: Testing and Inspection

AIR FUEL RATIO (A/F) SENSOR, HEATED OXYGEN SENSOR (HO2S) INSPECTION [LF, L3]

California Emission Regulation Applicable Model

NOTE:
- Before performing the following inspection, make sure to follow the troubleshooting flowchart. Foreword

A/F sensor current 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)
- A/F sensor current (PID: O2S11)

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 A/F sensor current (PID: O2S11) is 0.25 mA or more while decelerating as shown in the figure.

- If not within the specification, inspect the A/F sensor for an open or short circuit. Then if there is no malfunction in the wiring harness, replace the A/F sensor.

A/F sensor heater resistance inspection

1. Disconnect the A/F sensor connector.

2. Measure the resistance between A/F sensor terminals C and D.

- If not within the specification, replace the A/F sensor. Service and Repair

A/F sensor heater resistance
- 1-10 ohms

A/F sensor circuit open/short inspection (sensor)

1. Disconnect the PCM connector.

2. Disconnect the A/F sensor connector.

3. Inspect the following wiring harnesses for an 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.

- A/F sensor terminal A and PCM terminal 2AD
- A/F sensor terminal B and PCM terminal 2Z
- A/F sensor terminal C and PCM terminal 2BG
- A/F sensor terminal D and main relay terminal A

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

- A/F sensor terminal A and body ground
- A/F sensor terminal A and power supply
- A/F sensor terminal B and body ground
- A/F sensor terminal B and power supply
- A/F sensor terminal C and body ground
- A/F sensor terminal C and power supply
- A/F sensor terminal D and body ground

Front/rear 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)
- Front/rear HO2S voltage (PID: O2S12/O2S13)

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 front/rear HO2S outputs a voltage of 0.6 V or more, one time or more, then verify that the front/rear HO2S voltage (PID: O2S12/O2S13) 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. Then if there is no malfunction in the wiring harness, replace the front/rear HO2S.

Front/rear HO2S circuit open/short inspection (sensor)

- If not within the specification, replace the front/rear HO2S.

Front/rear HO2S heater resistance
- 2-50 ohms

Front/rear HO2S circuit open/short inspection (heater)

1. Disconnect the PCM connector.

2. 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.

- Front/rear HO2S terminal C and main relay A
- Front HO2S terminal D and PCM terminal 2BF
- Rear HO2S terminal D and PCM terminal 2BE

Short circuit
- If there is no continuity, there is a short circuit. Repair or replace the wiring harness.

Middle and rear
- Front/rear HO2S terminal C and body ground
- Front/rear HO2S terminal D and power supply
- Front/rear HO2S terminal D and body ground

Except for California Emission Regulation Applicable Model

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

A/F sensor current 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)
- A/F sensor current (PID: O2S11)

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 A/F sensoer current (PID: O2S11) is 0.25 mA or more while decelerating as shown in the figure.

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

- A/F sensor terminal A and main relay terminal A
- A/F sensor terminal B and PCM terminal 2AD
- A/F sensor terminal D and PCM terminal 2AC
- A/F sensor terminal E and PCM terminal 2BG*1, 2G*2
- A/F sensor terminal F and PCM terminal 2Z

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

- A/F sensor terminal A and body ground
- A/F sensor terminal B and body ground
- A/F sensor terminal B and power supply
- A/F sensor terminal D and body ground
- A/F sensor terminal D and power supply
- A/F sensor terminal E and body ground
- A/F sensor terminal E and power supply

*1
LF MTX, L3
*2
LF ATX

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: O2S12)

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: O2S12) 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. Then if there is no malfunction in the wiring harness, replace the HO2S.

HO2S circuit open/short inspection (sensor)

- If not within the specification, replace the HO2S. Service and Repair

HO2S heater resistance
- 2-50 ohms

HO2S circuit open/short inspection (heater)