I did replace the computer about 6-8 mos. Ago.
Now im getting tranny codes(1756-57)....i cant afford a rebuilt trans. At the moment, so my mechanic said he will replace the transducer and harness etc....my question is. Will I need to have the computer reflashed, or something ..or will it automatically fix itself when the sensor is put in??..2000 Durango 5.9L(currently shifting manually.dosent go into 3rd properly)

 

Replace the transducer and harness, and whatever else the codes are and do a correct PCM reset.

 

Which is unhooking the negative battery terminal, then turning and holding the key in the start position for at least 15 seconds, turn ignition off remove key and reconnect battery and your done

 

PCM can be reset once the transmission is fixed. No reflash required.

Those codes are the Governor Pressure Solenoid. That isn't a hard nor expensive replacement to see if it cures your problem(s.) $250 and done IIRC.

HTH,

IndyDurango