A MAP sensor measures the vacuum, which is the pressure inside the intake manifold of a running engine. As it is an important part in the healthy functioning of a vehicle, verifying it is crucial. Testing a MAP sensor will require the following: a multimeter, a vacuum pump, a wire piercing probe and a scan tool. First you should check if the sensor produces a signal. This should be done independently from the engine vacuum, using a vacuum pump. Next you should test whether the sensor is getting power with a multimeter. Then go on to checking the ground point of the circuit. Based on the results of these three simple tests you can asset whether you need to replace the MAP sensor or not.