Main Oxygen Sensor

Fig. 41 Oxygen Sensor Test Connections:

1. Start engine and warm-up to normal operating temperature.
2. Connect the positive (+) probe of a voltmeter to terminal VF of the engine check connector, and the negative (-) probe to terminal E1. Fig. 41
3. Run engine at 2,500 rpm for 90 seconds to preheat oxygen sensor.

Fig. 208 Check Connector And Service Wire:

4. Using a service wire, connect terminals T and E1 of the check connector, Fig. 208, while maintaining engine speed at 2,500 rpm.
5. Observe the number of times the voltmeter oscillates in 10 seconds.
6. If 8 or more oscillations occur, the oxygen sensor is operating normally. If less than 8 oscillations occur, proceed with testing procedure.
7. Disconnect terminals T and E1 and maintain engine speed at 2,500 rpm.
8. Measure voltage between terminals VF and E1. If voltmeter reads 0 volts, extract diagnostic codes and follow appropriate testing procedures.
9. If voltmeter reads more than 0 volts, replace the main oxygen sensor.
10. After replacement, repeat steps 3 - 6 and note oscillations. If zero oscillations occur with new oxygen sensor, replace ECU.


OXYGEN SENSOR HEATER

Fig. 42 Testing Oxygen Sensor Heater Resistance:

1. Engine and oxygen sensor must be cold, 68°F or less.
2. Disconnect the oxygen sensor from the electrical connector.
3. Using an ohmmeter, measure the resistance between terminals +B and HT. Fig. 42
4. The OS heater resistance should be 5.1 - 6.3 Ohms.
5. If not as specified, replace the oxygen sensor.