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 mod ule. If the air/fuel mixture ratio is richer than the theoretical air/fuel mixture ratio (i.e., if the concentration ot oxygen in the exhaust gas is sparse), a voltage of approximately lV 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 OV 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 ot 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 barometricpressure 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.)