Nissan Repair: map sensor, hand operated vacuum pump, vacuum leaks

Question
i have a 96 nissan maxima. the check engine light was on and 2 codes came up as map sensor, and egr valve. they were both replaced and the engine light is still on and coming up as the map sensor still. the vaccum hose on sensor is working but there is no power going into the sensor. what could be causing this problem? I had bought this car 2 weeks ago and have only had it for 3 days in my possession. its been in the shop and the mechanic is not able to figure it out. please help

Answer
Hi there,  if there is no voltage to the MAP (Manifold Absolute Pressure Sensor), it is because one of the wires is open or damaged. The on board computer is unable to receive a signal from the sensor. The computer sends a low voltage to the MAP of usually 5 or 8 volts dc and another wire is used to ground the MAP. That wire is also critical. The mechanic should check for continuity between the computer's terminal that sends that voltage to the sensor and the other end that terminates at the MAP. If there is no continuity, then the wire is damaged. If there is continuity, then the ground wire should be checked. There is a possibility that the computer fails to ground the circuit or it fails to send a voltage to it. In this case the computer needs to be replaced. As the vacuum increases, the voltage reading decreases. The mechanic should also check for vacuum leaks in other areas of the engine. To run the tests, the mechanic will need a hand operated vacuum pump, a digital multimeter and a hatpin or a paper clip to insert it in the sensor's connector, (at the hot wire) for voltage check without disconnecting it.