QUESTION:
Recently my check engine light came on and a mechanic read the code and it came up P1400 which is the manifold differential pressure sensor circuit. I have a 2000 Mitsubishi Galant; does this need to be repaired by a Mitsubishi dealer or can I take it to any auto repair facility?
ANSWER:
P1400 is an MDP sensor. on turbo equipped engines a special sensor is used to measure manifold pressure (MDP=Manifold differential pressure)...or the difference between manifold pressure and barometric pressure. the engine controller has seen values outside of what is programmed normal and therefore set the code. manifold pressure sensing is critical to fuel management. if the sensor is remote mounted and has a hose going to it...check the hose for splits, holes, soft places that might collapse, kinks or anything else that might prevent the pressure signal from reaching the sensor. if it's not that simple...you may a have a failed sensor or engine controller. to sort that out you need to do some specific pinpoint testing using the trouble tree for that code plus a DVOM...at the very least.
Most auto mechanics would probably just change the sensor and send you on your way, after charging you a hefty fee for the part. If it were my car I'd check for vacuum leaks everywhere, including all devices that use vacuum (especially the ones going to the sensor). While it could be a bad sensor just the same, I have a suspicion that the code is giving you a symptom and the real problem might be a vacuum leak or valve cover gasket, etc.
