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AIR FUEL RATIO (A/F) SENSOR, HEATED OXYGEN SENSOR (HO2S) INSPECTION [L8, LF, L3]

id0140a5899800

  Note

  • Before performing the following inspection, make sure to follow the troubleshooting flowchart. (See FOREWORD [L8, LF, L3].)

## A/F Sensor Current Inspection

1. Warm up the engine to normal operating temperature.

2. Using the WDS or equivalent, 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. (See A/F sensor circuit open/short inspection (sensor).) 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 2B and 2D.

  • If not within the specification, replace the A/F sensor. (See EXHAUST SYSTEM REMOVAL/INSTALLATION [L8, LF, L3 2WD].) (See EXHAUST SYSTEM REMOVAL/INSTALLATION [L3 4WD].)

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 1A and PCM terminal 2AD
  - A/F sensor terminal 1B and PCM terminal 2AC
  - A/F sensor terminal 1C and PCM terminal 2Z
  - A/F sensor terminal 2B and main relay terminal C
  - A/F sensor terminal 2D and PCM terminal 2BG

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 1A and body ground
  - A/F sensor terminal 1A and power supply
  - A/F sensor terminal 1B and body ground
  - A/F sensor terminal 1B and power supply
  - A/F sensor terminal 1C and body ground
  - A/F sensor terminal 1C and power supply
  - A/F sensor terminal 2B and body ground
  - A/F sensor terminal 2B and power supply
  - A/F sensor terminal 2D and body ground
  - A/F sensor terminal 2D and power supply

## HO2S voltage inspection

1. Warm up the engine to normal operating temperature.

2. Using the WDS or equivalent, 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. (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 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 terminal A and PCM terminal 2Q
  - HO2S terminal B and PCM terminal 1BC

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

  - HO2S terminal A and body ground
  - HO2S terminal A and power supply
  - HO2S terminal B and power supply

## HO2S heater resistance inspection

1. Disconnect the HO2S connector.

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

  • If not within the specification, replace the HO2S.

HO2S heater resistance

  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 terminal C and ignition switch
  - 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.
Rear

  - HO2S terminal C and body ground
  - HO2S terminal D and power supply
  - HO2S terminal D and body ground