So far still kinda stumped. I can't get anything to work. At times the truck works fine other time it acts up very badly. Everything i have tried testing seems good. Only thing i haven't done is replaced the pcm or burnt the dam truck

 

Since it comes and goes randomly, definetly sounds like an electrical issue. Another thing to check is all of the frame and body grounds. A loose or corroded ground will send the electronics into chaos! There should be frame to body, battery to frame and bed to frame grounds. If you live in the rust belt, I would lay good money on that being the problem.

 

I changed all battery cables, engine to frame ground, body to frame ground, body to battery ground and even added a few grounds. The truck only does it when it's warmed up and feels like it

 

I can drive the truck to work 3 miles restart it and everything works i drive it 30 miles to pick up my side by side at the dealer and no overdrive. The next time i go to the dealer i have over drive. So i drive it next town over to help a friend turn the truck off for 5-10 min restart it no overdrive. Won't ever act up cold has to be at operating temp and not in a good mood that day

 

Thats the worst kind of problem to have! LOL! I'm an electrician by trade, and get calls all the time where it wasn't working until I get there, then they can't make it do it again for nothing! LOL! Had a call yesterday at a commercial door plant saying that there lights and computers wouldn't work when they came in that morning, by the time I got there, everything was working fine. Standing around bs'ing about diesels and Jeeps, the lights dimmed for about 10 seconds, then came back on. Put my meter on the service and set to record, finally about 20 minutes later, it did it again. Voltage dropped down to 40 volts, should have been 120, called the utility company out, there meter guy said everything was find on their end. About 10 minutes later it droppped again, he changed his tune, it was on their end. They had made a bad splice at the transformer!

 

Drove it to work today and drove it on lunch and when I started it after lunch tach went nuts and then died again . Kinda getting funny just so tired of messing with it.

 

These problems are my favorite! I find when I get into electrical in real depth it gets a little jumbled and confusing.
if you would like. PM me and I will have you call me. I would be willing to help. When we get the issue resolved I will write a synopsis on the subject

 

As of now these not much to try besides a pcm or fire . Checked every ground and almost every wire i could find. Changed the crank sensor and vehicle speed sensor. Had the alt checked added a few ground wires changes some wire ends. Checked for crusty plugs and pins in the plugs. Thinking pcm or fire

 

Is the pcm in a location you can get to fairly easy? If so while the truck is running, and the tach is dead, wiggle the connector and/or tap on the box with a rubber mallet. If it clears up, or momentarily starts working, then you have got it narrowed down to the pcm or connector. If it has been chipped, they may have not seated the chip on the circuit board well.

 

im having a similar problem except mine is a 97 12v and its a manual my tach isnt working neither is the GEN so i been reading and the forums keep saying that its the sensor except its getting power just not reading ive gaped many times to see what was wrong but cant figure it out