A GMC Truck Oxygen Sensor is a hollow tube which is divided into three compartments by a U-shaped platinum-coated rod.
To avoid such problems, it is recommended that you constantly check your Auto Parts and should you replace it with a new one, the best place to find quality replacement parts is through the Internet.
In case yours is damaged or ruined, be sure that you replace it immediately; the market offers wide variety of Online Part replacements.
To be more precise, if the mixture is too rich or too lean, the GMC Truck Oxygen Sensor adjusts the amount of fuel that enters your engine accordingly.