Upstream Sensor

1. Disconnect the heated oxygen sensor connector.
2. Check that there is continuity between terminal 1 and terminal 3 on the heated oxygen sensor connector.
3. If there is no continuity, replace the heated oxygen sensor.
4. Warm up the engine until engine coolant is 8000 (176°F) or higher.
5. Use the jumper wires to connect terminal 3 of the heated oxygen sensor connector to the battery (+) terminal and terminal 1 to the battery (-) terminal.

CAUTION: Be very careful when connecting the jumper wires, or the heated oxygen sensor can be damaged.

6. Connect a digital voltage meter between terminal 2 and terminal 4.
7. While repeatedly racing the engine, measure the heated oxygen sensor output voltage.

Standard value: If you make the air/fuel ratio rich by racing the engine repeatedly, a normal heated oxygen sensor will output a voltage of 0.6 - 1.0 V.

8. If the sensor is defective, replace the heated oxygen sensor.