Oxygen Sensor: Testing and Inspection

Vehicle Harness Check
1. Check for open and short circuit in harness & connector faults between the O2 sensor and ECM.
2. Check for approximately 12V between heater harness

Heater Resistance Check
1. Verify that the resistance between the heater terminals is between 4 Ohms and 10 Ohms at -20°C to 100°C.

Performance Check
1. Run the engine at 2500 RPM for two minutes to heat up the O2 sensor.
2. Check the voltage of the sensor output: Alternates between less than 0.4V at feed back engine conditions and in excess of 0.5V, see graph.

These voltages are for reference only:

3. Check that cycle of the upstream sensor output is in accordance with the appropriate pinpoint test.
4. Check that cycle of the downstream sensor output is in accordance with the appropriate pinpoint test.