AIR FUEL RATIO (A/F) SENSOR INSPECTION [L8, LF]


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Note
• Before performing the following inspection, make sure to follow the procedure as indicated in the troubleshooting flowchart. (See Troubleshooting Procedure.)

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. (See A/F Sensor Circuit open/short Inspection.) Then if there is no malfunction in the wiring harness, replace the A/F sensor. (See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [L8, LF].)

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. (See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [L8, LF].)
A/F sensor heater resistance
1-10 ohms

A/F Sensor Circuit open/short Inspection

1. Disconnect the PCM connector. (See PCM REMOVAL/INSTALLATION [L8, LF].)

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