jeeptjstud

1996 Cummins 12V 2500 4WD with 110k miles. Driving down the road and all of a sudden GEN light came on, kicked out of overdrive into drive with O/D light on and will no engage. Stays locked in 3rd gear now.

Was on a road trip so I wired up an external temporary voltage regulator after replacing the alternator and batteries. Got the truck home, and the PCM fuse is blown, all other relays and fuses are good.

Replace governor pressure solenoid/pressure sensor--no fix
Replaced PCM--no fix

I can put a new PCM fuse in and the truck will run fine until the fuse blows after 10-200 miles of driving. It varies each time. At which time the transmission goes into third gear, overdrive light comes on and will not engage into any other gear. I have went through the entire wiring harness with no luck.

This truck has been garaged since new and taken extremely good care of. I have no idea where to go from here.

AlpineRAM

Maybe the wire controlling the AC pressure sender is chafed and shorts to ground.

Fooled me once on a car, no rime or reason when it blew the PCM fuse.

texasprd

Since there are significant variances in mileage between occurrences, it does look like an intermittent short somewhere may be possible, as AlpineRam suggests. Got a good high input impedance multimeter and a factory service manual or other source to wiring diagrams, like AllDataDIY?

Sending PM to OP...