What is the reason why the three-wire throttle circuit of an automobile has two grounding wires?

There must be a short circuit to ground. One of the wires is grounded. One of the three wires is a ground wire, a 5V power supply and a signal wire. The signal line voltage measured by multimeter should not be higher than 5V! 5V power supply is generally the same as water temperature sensor! It's all supplied by computers! If there is no short circuit to the ground, it is a short circuit inside the computer! Is that the computer is broken!