Oxygen Sensor: Testing and Inspection
Heated Oxygen Sensor Circuit:
Oxygen Sensor Testing:
Oxygen Sensor Conditions:
Oxygen Sensor Testing:
O2 SENSOR TEST
1. Start and warm the engine until the coolant temperature exceeds 80°C (176°F).
2. Connect a volt meter (with at least 10 megaohm resistance) to sensor terminal A1 (do not disconnect the connector).
3. Accelerate the engine in second gear (M/T) or L range (A/T) to 3500 RPM at wide open throttle.
Voltage: Approximately 600 - 1,000 mV.
4. Faulty results in the above test may be caused by:
a. Engine mechanical problems
b. Open or shorted wiring harness
c. Fuel pressure
d. Fuel mixture
5. Perform all tests before replacing the sensor.
O2 SENSOR HEATER TEST
1. Test heater function at cold engine temperatures
2. Disconnect the O2 sensor connector.
3. Using an ohm meter, check for continuity between O2 sensor connector terminals A3 and A4.
Continuity: Should exist
4. Connect a volt meter to oxygen harness connector terminal A3.
5. Start engine and measure voltage at idle.
Voltage: System Voltage.
NOTE: After warm-up, No voltage will be present.
5. Raise engine speed to 5000 RPM and measure voltage.
Voltage: 0 Volts.
Osciloscope Test:
OSCILLOSCOPE TEST
1. Connect scope pickup probe to the sensor terminal A1.
2. Warm engine to operating temperature and keep it running at 2,000 RPM, check the waveform on the scope. If scope pattern is not as depicted in image, the sensor may be bad or there could be a fuel mixture problem. Refer to Computers and Control Systems/System Diagnosis/Diagnosis by Symptom for further system troubleshooting before replacing the assembly. Symptom Related Diagnostic Procedures
HARNESS TEST
Oxygen Sensor:
Oxygen Sensor:
1. Disconnect the oxygen sensor and the ECM connectors.
2. Using an Ohmmeter, check for continuity between the ECM harness connector terminal 55 and the oxygen sensor harness connector terminal A1.
Continuity: Should exist.
3. Using an Ohmmeter, check for continuity (short) to ground between the ECM harness connector terminal 55 and the oxygen sensor harness connector terminal A1.
Continuity: Should not exist.
4. Using an Ohmmeter, check for continuity between the ECM harness connector terminal 72 and the oxygen sensor harness connector terminal A2.
Continuity: Should exist.
5. Using an Ohmmeter, check for continuity between the oxygen sensor harness connector terminal A4 and ground.
Continuity: Should exist.
If any of the previous tests produce unsatisfactory results, the harness will need to be repaired or replaced. Once repairs have been completed, clear the trouble codes and road test the vehicle to confirm that the repair has corrected the problem and the code doesn't return.
If the same trouble code reoccurs, it is possible that there is an intermittent failure of the component or the ECM. Check for looseness at all harness junctions and test for an intermittent failure.
SCAN TOOL TESTING
Front Oxygen Sensor:
Front Oxygen Sensor
Rear Oxygen Sensor:
Rear Oxygen Sensor
Front Oxygen Sensor:
Oxygen Sensor Heater