Bad PCM?

C

cottondoc

new to site
I was driving my 1995 the other day and while going down the road the tach and speedo stopped working. All other gauges continue to work normally. The truck then dropped out of overdrive. I assume because the transmission lost pcm input, but I'm not sure. I cut the truck off and then back on. The tach and speedo started working again, but cut off again in just a few miles. I haven't been able to get them to work since. I checked the PCM connections, and they seem to be intact. It continues to not shift into overdrive since the tach and speedo quit. I can lock the converter with my lockup switch, but it no longer locks on its own. Any thoughts? Maybe a replacement pcm would fix it? How much are used PCMs for a 1995 with 47rh going for?

The truck is a 1995 regular cab, 4x4 with the 47rh. I probably need to update my sig but it has a Darren Morrison built all billet shaft trans, 5x18 injectors, 366 over 480 compounds and a mildly built 215 pump on the original short block. Thanks in advance for any information.


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Since the speedo stopped working the engine speed sensor theory isn't likely. If you lost cruise control, tach and alternator (gen light) that would point to the ESS. There are several grounds under the hood that I would remove, inspect, clean and reinstall. They are all shown in the factory service manual.
 
Sounds like I have several things to check. I'll have to time to give it a good look this weekend. Thanks again to everyone for all good info


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Just got the truck fixed. It was the crank position sensor. New crank position sensor installed and all is working good again. Thanks for everybody's input.


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