The throttle is the part of the fuel injection system that opens and closes the access to air. It is controlled by the accelerator pedal and can cause combustion to increase or decrease depending upon the demand placed on the engine. Throttle position is important to the engine control unit in determining the correct amount of fuel to inject for the proper ratios. It is also important in the timing of the combustion. Many parts must work together to get the engine to run smoothly and according to the demands of the driver and the terrain the car is going over. The throttle is integral in determining how the timing should run. The throttle position sensor sends information about the position of the throttle to the central computer so that all the other systems can be timed correctly. When the throttle position sensor malfunctions, many other systems will not function well either.