Component Tests and General Diagnostics
HEATED OXYGEN SENSOR (HO2S) INSPECTIONNOTE: Before performing the following inspection, make sure to follow the troubleshooting flowchart. (See FOREWORD.) Flow of Diagnosis
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: O2S11/O2S12/O2S21/O2S22)
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: O2S11/O2S12/O2S21/O2S22) 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 Middle/rear 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. 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 A and PCM terminal 18
- HO2S (RF) terminal B and PCM terminal 20
- HO2S (LF) terminal A and PCM terminal 19
- HO2S (LF) terminal B and PCM terminal 20
- HO2S (RR) terminal A and PCM terminal 44
- HO2S (RR) terminal B and PCM terminal 20
- HO2S (LR) terminal A and PCM terminal 45
- HO2S (LR) terminal B and PCM terminal 20
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 GND
- HO2S (RF) terminal B and power supply
- HO2S (LF) terminal A and power supply
- HO2S (LF) terminal A and body GND
- HO2S (LF) terminal B and power supply
- HO2S (RR) terminal A and power supply
- HO2S (RR) terminal A and body GND
- HO2S (RR) terminal B and power supply
- HO2S (LR) terminal A and power supply
- HO2S (LR) terminal A and body GND
- 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.
- if not within the specification, replace the HO2S.
HO2S heater resistance
HO2S (RF, LF) heater: 2 - 20 ohms
HO2S (RR, LR) heater: 2 - 50 ohms
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.
- HO2S (RF) terminal C and ignition switch
- HO2S (RF) terminal D and PCM terminal 83
- HO2S (LF) terminal C and ignition switch
- HO2S (LF) terminal D and PCM terminal 84
- HO2S (RR) terminal C and ignition switch
- HO2S (RR) terminal D and PCM terminal 57
- HO2S (LR) terminal C and ignition switch
- HO2S (LR) terminal D and PCM terminal 58
Short circuit
- If there is no continuity, there is a short circuit. Repair or replace the wiring harness.
- HO2S (RF) terminal C and body GND
- HO2S (RF) terminal D and power supply
- HO2S (RF) terminal D and body GND
- HO2S (LF) terminal C and body GND
- HO2S (LF) terminal D and power supply
- HO2S (LF) terminal D and body GND
- HO2S (RR) terminal C and body GND
- HO2S (RR) terminal D and power supply
- HO2S (RR) terminal D and body GND
- HO2S (LR) terminal C and body GND
- HO2S (LR) terminal D and power supply
- HO2S (LR) terminal D and body GND