Oxygen Sensor

Operation

The oxygen sensor functions to detect the concentration of oxygen in the exhaust gas; it converts those data to Voltage, and inputs the resulting signals to the engine control module. If the air/fuel mixture ratio is richer than the theoretical air/fuel mixture ratio (i.e., if the concentration of oxygen in the exhaust gas is sparse), a Voltage of approximately 1 V is output; if the air/fuel mixture ratio in leaner than the theoretical air/fuel mixture ratio (i.e., if the concentration is dense). a Voltage of approximately 0 V is output.

The engine control module, based upon those signals, regulates the amount of fuel injection so that the air/fuel mixture ratio becomes the theoretical air/fuel mixture ratio.


Troubleshooting Hints

Hint 1:

The exhaust gas purification performance will worsen if there is a malfunction of the oxygen sensor.

Hint 2:

If the oxygen sensor output Voltage deviates from the standard value even though the results of the checking of the oxygen sensor are normal, the cause is probably a malfunction of a component related to mixture control.

Examples:

(1) Malfunction of an injector.
(2) Air leakage into the intake manifold from a leaking gasket.
(3) Malfunction of the volume air flow sensor, the intake air temperature sensor, the barometric pressure sensor, or the engine coolant temperature sensor.





Inspection




Harness Inspection


Sensor Inspection


Caution:

1. Before checking, warm up the engine until engine coolant temperature reaches 85 to 95°C (185 to 205°F).
2. Use an accurate digital Voltmeter.










(1) Disconnect the oxygen sensor connector and connect a Voltmeter to the oxygen sensor connector.
(2) While repeating engine racing, measure the oxygen sensor output Voltage.


Oxygen sensor installation torque: 40-50 Nm (30-36 ft.lbs.)