I met someone who knows of a 95 2500 for sale. He said it has a "computer problem". They apparently did some work on the truck and now the tranny won't shift into overdrive and the glowplug light won't come on. He said it will need a new computer. I've yet to speak to the owner so I'm not sure what to think. Any thoughts from you wise sages out there?

 

The computer (PCM) is a stout unit that rarely goes bad and has internal circuit protection. Expect to pay about $600 for a new one from the dealer.
Most often the problem is a wiring problem rather than the PCM itself.

 

I found this out after paying $600+ for a PCM for my 97 back in November. Turned out the CPS was shorting out the PCM. If you have no Tach, no MIL light no Speedo, no Alternator charging then it could be a bad CPS for about $75. Mine was not an Auto tranny.

What other symptoms do you have? What dash panel gages and lights don't work? Does key on give you all the gage check functions with the MIL for a few seconds or not? That's what my bad CPS did.