Chrysler Repair: 96 dodge intrepid 3.5 pcm/ code 31, crankshaft sensor, obd ii

Question
hi
  my pcm when bolted in the way it should be, engine rotates but wont start...when i undue pcm and lay it flat and loose in there car will start but at 2000 rpm it starts reving high and low speedometer goes crazy check engine light comes on and gives me a code 31 and transmission gears are all mixed up. just put in a new crankshaft sensor and have checked all voltage on sensors
car did this while driving...any suggestions appreciated

Answer
Hi Jerrick,
The 31 code is about the evap system purge solenoid circuit having an electrical problem (open or shorted). I doubt that explains the problem. The transmission gear problem is probably limp-in mode which the trans does when it detects a problem that if allowed to go without service would produce more damage to the trans. It put the trans in 2nd and will not allow it to shift. I would suggest that you get a fault code readout using an OBD-II fault code reader plugged in under the dash. If you can get it to an Autozone parts store they will often do the readout for free. Or an independent shop will do it for $40 or so. Let me know if you get some 4-digit codes as the result of the readout.
The pcm operating differently when installed/uninstalled suggests that there is some flaky wire connection in the cables to the pcm, or a problem with the plug pin/socket interfacea. You may want check continuity on all those wires, though it is a big job.
Roland