| DETECTED CONDITION | POSSIBLE CAUSE |
| The sensor voltage should be the following and less after warming up condition. (Sensor Voltage ≤ 0.4 V) | • HO2 sensor or its circuit open or short. • Fuel system malfunction. • ECM malfunction. |
Inspection
Step 1
1) Lift and support the fuel tank. (5-7)
2) Turn the ignition switch OFF.
3) Check the HO2 sensor coupler for loose or poor contacts.
4) Insert the needle pointed probes to the HO2 sensor coupler.
5) Turn the ignition switch ON and measure the heater voltage between O/W wire (ECM side) and ground.
6) If the tester voltage indicates the battery voltage for few seconds, it is good condition.
- Heater voltage: Battery voltage (O/W - Ground)
Note: Battery voltage can be detected only during few seconds after ignition switch is turned ON.
- 09900-25008: Multi circuit tester set
- 09900-25009: Needle pointed probe set
- Tester knob indication: Voltage (⎓)
Is the voltage OK?
| YES | Go to Step 2 |
| NO | Replace the HO2 sensor with a new one. |
Step 2
1) Warm up the engine enough.
2) Insert the needle pointed probes to the HO2 sensor coupler.
3) Measure the HO2 sensor output voltage at the coupler (between W/G and B/Br wires) when idling condition.
4) Also, measure the HO2 sensor output voltage while holding the engine speed at 5 000 r/min.
- HO2 sensor output voltage at idle speed: 0.4 V and less ((+) W/G - (-) B/Br)
- HO2 sensor output voltage at 5000 r/min: 0.6 V and more ((+) W/G - (-) B/Br)
- 09900-25008: Multi circuit tester set
- 09900-25009: Needle pointed probe set
- Tester knob indication: Voltage (⎓)
Is the voltage OK?
| YES | Go to Step 3 |
| NO | Replace the HO2 sensor with a new one. |
Step 3
1) Turn the ignition switch OFF.
2) Disconnect the HO2 sensor coupler.
3) Check the resistance between the terminals (White - White) of the HO2 sensor.
- HO2 heater resistance: 4-5 Ω (at 23°C/73.4°F) (White - White)
Notes:
- Temperature of the sensor affects resistance value largely.
- Make sure that the sensor heater is at correct temperature.
- 09900-25008: Multi circuit tester set
- Tester knob indication: Resistance (Ω)
Is the resistance OK?
| YES | • W/B, O/G, W/G or B/Br wire open or shorted to ground, or poor (8), (9), (24) or (34) connection. • If wire and connection are OK, intermittent trouble or faulty ECM. • Recheck each terminal and wire harness for open circuit and poor connection. |
| NO | Replace the HO2 sensor with a new one. |
