Oxygen Sensor: Testing and Inspection

HEATED OXYGEN SENSOR
Functional Inspection

View: Heated Oxygen Sensor Test Connections:

1. Warm engine to operating temperature and run at idle.
2. Unplug sensor connector.
3. Connect voltmeter across terminals A+ and B-.
4. Run engine at 4500 rpm until voltmeter indicates approximately 0.7 Volts.
5. Measure voltage while increasing and decreasing engine speed suddenly several times.

View: Heated Oxygen Sensor Test Specifications:

6. Voltage should be greater than 0.5 Volts when accelerating and less than 0.4 Volts when decelerating.

View: Special Service Tools:

7. Connect Mazda System Selector and Self-Diagnosis Checker (or aftermarket equivalents) to data link connector. Set switch A to position 1 and TEST SW to 02 MONITOR.

NOTE: With brake pedal depressed, monitor lamp shows operation of right sensor. With brake pedal released, monitor lamp shows operation of left sensor.

8. Increase engine speed to between 2000 and 3000 rpm and verify that monitor light flashes for 10 seconds.
9. Repeat tests for opposite side sensor. If not as specified, replace sensor(s).

INTEGRAL SENSOR HEATER
Resistance Check

View: Checking Sensor Heater Resistance:

1. Shut engine off, allow sensor to cool and connect ohmmeter between sensor connector terminals C and D. Check that heater resistance is approximately 13 ohms @ 20°C (68°F).
2. Replace sensor if resistance is not as specified.
3. Repeat test for opposite side sensor.