C 3500 Truck 2WD V8-454 7.4L VIN J SFI (1999)
Oxygen Sensor: Description and Operation
Heated Oxygen Sensor (Cutaway View)
Due to emissions regulations, the vehicle must enter closed loop as soon as possible. By heating the individual oxygen sensors, they reach their activation
temperature sooner than those without heaters. Once an oxygen sensor reaches the activation temperature, the sensor is able to monitor the oxygen
content of the exhaust more accurately. The vehicle operates in closed loop status once activation temperature is reached. Thus, the VCMs fuel trim
corrections reduce the vehicle's total emissions. Vehicles produce less emissions when they are in closed loop than in open loop.
The heated oxygen sensors are mounted in the exhaust system where they can monitor the oxygen content of the exhaust gas stream. The oxygen present
in the exhaust gas reacts with the sensor to produce a voltage output. This voltage should constantly fluctuate from approximately 100 mV (high oxygen
content - lean mixture) to 900 mV (low oxygen content - rich mixture).