Century L4-2.2L VIN 4 (1994)
Oxygen Sensor: Description and Operation
Oxygen Sensor Circuit
PURPOSE:
The oxygen (O2) sensor measures the oxygen content of the exhaust. The PCM monitors the sensor to maintain air/fuel mixture of 14.7 to 1.
OPERATION:
The oxygen sensor monitors atmospheric air versus exhaust gas oxygen content 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). By monitoring the oxygen sensor output voltage, the
computer can determine the amount of oxygen in the exhaust gas and adjust the air/fuel mixture accordingly, this is known as "CLOSED LOOP"
operation.
When the sensor is cold it is like an open circuit and produces no voltage below 600°F (315°C). An open sensor circuit or cold sensor causes
"OPEN LOOP" operation.
The heated oxygen sensor works in the same manner as the non-heated oxygen sensor. The exception is that B+ is supplied to a heating unit that is
part of the sensor itself. This heater receives voltage from the generator charging circuit. The heater helps the PCM control the fuel injection
sooner for better fuel emissions. There are no malfunction Codes to detect if the heater part of the sensor is working.
LOCATION:
Exhaust Manifold
