In fresh engines, Oxygen sensors are typically located on the exhaust system.
In the early 1980s, automobile manufacturers began incorporating oxygen sensors, or "02" sensors, in the computerized monitoring systems of their vehicles. These sensors help the computers sense how well the engine is performing by monitoring the oxygen levels in the exhaust. In GMC vehicles, as with any vehicle that contains an O2 sensor, there are a few distinct problems that can be caused if the sensor becomes faulty.
The computer detects this loss of signal and switches to an "open loop" mode of operation, in which the computer directs a pre-programmed fuel and air mixture into the engine. This pre-programmed mixture setting is intended to allow the vehicle to continue to be driven in the event of component failures until repairs can be made. This open loop setting results in an overly rich fuel mixture and significantly higher fuel consumption.
The result is increased emissions levels and poor mileage.
High fuel consumption
When an O2 sensor fails, it can no longer detect the oxygen levels in the airstream or send a signal to the vehicles onboard computer.
Increased emissions
As an O2 sensor ages and accumulates contaminates on its surface, it becomes less responsive to changes in the oxygen levels in the engine's exhaust. At the same time, the electrical current level sent out by the sensor may be weaker than normal, which causes the vehicle's onboard computer to make improper adjustments to the fuel and air mixture entering the engine.Stalling-Hesitation
A faulty O2 sensor can result in the engine running with an overly rich fuel and air mixture that contains a larger-than-normal amount of fuel and can cause the catalytic converter connected to the exhaust system to overheat. This overheating can cause the catalyst material within the catalytic converter to melt and form an obstruction within the converter, causing an increase in exhaust back-pressure and resulting in hesitation and stalling of the engine.
