Oxygen Sensor

Operation

The heated 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 1V is output; if the air/fuel mixture ratio in leaner than the theoretical air/fuel mixture ratio (i.e., it 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.

Battery power supply is applied, by way of the multiport fuel injection relay, to the oxygen sensor heater. As a result, the sensor element is heated by the heater, so that the heated oxygen sensor shows excellent response even if the temperature of the exhaust gas is low.

Troubleshooting Hints

HINT 1: The exhaust gas purification performance will worsen if there is a malfunction of the heated oxygen sensor.

Hint 2: If the heated oxygen sensor output Voltage deviates from the standard value even though the results of the checking of the heated 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


(1) Disconnect the heated oxygen sensor connector, and connect the special tool (harness connector) to the heated oxygen sensor side.





(2) Check that there is continuity [approx. 12Q at 2O~C (68~F)] between heated oxygen sensor connector terminal � (red clip of special tool) and terminal 04 (blue clip).
(3) If there is no continuity, replace the heated oxygen sensor.
(4) Warm up the engine until the engine coolant temperature exceeds 80°C (176"F).





(5) Use jumper wires to connect heated oxygen sensor terminal � (red clip of special tool) and terminal 04 (blue clip) to the battery 0+ terminal and 0- terminal.

Caution: Be very careful when connecting the jumper wires because the heated oxygen sensor will be damaged if a mistake is made in the connecting terminals.

(6) Connect a digital Voltmeter between terminal 01 (yellow clip of special tool) and terminal � (black clip).





(7) While repeatedly racing the engine, measure the output Voltage of the heated oxygen sensor.