Cavalier/Z24 L4-138 2.3L DOHC VIN D MFI (1995)
Oxygen Sensor: Description and Operation
Fuel Control Oxygen Sensors
Exhaust Oxygen Sensor (02)
DESCRIPTION
The Oxygen Sensor (O2S) is mounted in the exhaust system where it can monitor the oxygen content of the exhaust gas stream. The oxygen
content in the exhaust reacts with the sensor to produce a voltage output. This voltage ranges from approximately 0.1 volt (high oxygen - lean
mixture) to 0.9 volt (low oxygen - rich mixture). This voltage can be measured with a digital voltmeter having at least 10 megohms input
impedance. Use of standard shop type voltmeters will result in very inaccurate readings.
By monitoring the voltage output of the O2S, the PCM will know what fuel mixture command to give to the injectors.
Lean mixture-low O2S voltage = rich command.
Rich mixture-high O2S voltage = lean command.
The O2S, it open, should set a DTC P0134. A constant low voltage in the sensor circuit should set a DTC P0131. A constant high voltage in the
circuit should set a DTC P0132. DTCs P0131 and P0132 could also be set as a result of fuel system problems. See DTC charts for conditions that
can cause a lean or rich system. See: Testing and Inspection
