Without Scan Tool

Heated Oxygen Sensor Circuit:

Engine Control Module Connector--For Pin Applications See Components:

NOTE: Perform all tests before replacing the sensor.

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 the #1 terminal at the sensor (do not disconnect the connector).
3. Operate the engine at 4000 rpm and quickly lower the engine to idle.

Voltage:
Approximately 200 mV or lower.

4. Operate the engine at idle and observe the volt meter.

Voltage:
Should vary between between 400 mV or lower and 600 mV.

5. Operate the engine at 2000 rpm and observe the volt meter.

Voltage:
Should vary between between 400 mV or lower and 600 mV.

6. 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

O2 SENSOR HEATER TEST
1. Disconnect the O2 sensor connector.
2. Using an ohm meter, check for continuity between O2 sensor connector terminals 3 and 4.

Continuity Should Exist

Osciloscope Test:

OSCILLOSCOPE TEST
1. Connect scope pickup probe to the sensor terminal 1.
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 diagnosis by symptom for further system troubleshooting before replacing the assembly.

Oxygen Sensor Testing:

HARNESS INSPECTION