Mitsubishi Repair: Engine Computer Codes / Trans, differential pressure sensor, differential pressure switch

Question
I have a 1996 Galant (auto) with 145K that the check engine light came on.  I had a mechanic read the code and it came up P1400.  He didn't have the mitsubishi info so he couldn't help much more.  He cleared it and it went away for about 5 days and came back.  Second,  when the transmission is in Drive and the car and temp is less than 40 F it does not want to shift and bogs down and then seems to catch and jerk forward.  When it warms up or when it is still cold and in 2 or 1 it is fine.  It has been >40k since it was serviced last.

Answer
Eric,
Code 1400 for your car refers to the 'Manifold Differential Pressure Sensor Malfunction'.  Manifold differential pressure switch converts the intake manifold plenum pressure to the voltage and inputs to the engine control
module (ECM - the car's computer). ECM confirms the operation of EGR system from this signal and, if there is any error in the EGR system, memorizes the diagnostic trouble code and displays the check engine light .

In short, this sensor is used for emissions reasons, and most car's emissions systems are extremely sensitive, and the EGR valve or intake manifold may just need to be cleaned out.  Also, have your PCV valve replaced.  Then, have your ECM reset to turn off the check engine light.
Good luck!