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Rear Heated Oxygen Sensor

REAR HEATED OXYGEN SENSOR (HO2S) INSPECTION[LF]

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

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)
- Rear H025 voltage (PID: 02S12)
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 rear HO2S outputs a voltage of 0.6 V or more, one time or more then verity that the rear HO2S voltage (PID: 02S12) is 0.3 V or less while decelerating as shown in the figure.
- If not within the specification, inspect the rear H025 for an open or short circuit.Then if there is no malfunction in the wiring harness, replace the rear HO2S.

Rear HO2S Heater Resistance Inspection




1. Disconnect the rear H025 connector.
2. Measure the rear H025 resistance between terminals C and D.
- If not within the specification, replace the rear H025.

Rear HO2S heater resistance
2-50 ohms

Rear HO2S Circuit Open/Short Inspection










1. Disconnect the PCM connector.
2. Disconnect the rear 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.
- Rear HO2S terminal A and PCM terminal 2Q
- Rear HO2S terminal B and PCM terminal 2BH
- Rear HO2S terminal C and ignition relay
- Rear HO2S terminal D and PCM terminal 2BE

Short circuit
- If there is continuity in the following wiring harnesses, there is a short circuit. Repair or replace the wiring harness.
- Rear HO2S terminal A and power supply
- Rear HO2S terminal A and body ground
- Rear HO2S terminal B and power supply
- Rear HO2S terminal B and body ground
- Rear HO2S terminal C and body ground
- Rear HO2S terminal D and power supply
- Rear HO2S terminal D and body ground
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