Trans or PCM issue?

[biggy238]

My 96 is doing something I can't fully explain.
It is going neutral in gear, and the only thing I have noticed that coincides is the volt meter being at 12v rather than 14v like it should be.
I think this ties in with the grid heater function as it seems to be shortly after I start the truck.

The other issue is that several times while running ~80mph (according to the GPS) on my way home the transmission was trying to drop out of overdrive, and judging by how high it was trying to Rev, I think it was trying to downshift to 2nd.

The only other time I had it downshift like that was when I had first bought the truck and a battery cable was dead shorting the entire electrical system.

Plenty of good clean transmission fluid in it.

I think it's the electrical supply to the PCM but what specifically should I look for? I'm curious about the excitation of the alternator and the fact that the voltage stays low as long as it does.

I do have a pot for TPS and the percentage is pretty high. It isn't attempting to shift OD until 60mph right now.

Thanks for any input
Kyle

 

[biggy238]

Bump

 

[biggy238]

I drove it to work this morning. I set the TPS back to where I usually drive it, about 30 percent.
It was trying to freewheel in OD cruising at about 50mph. It did that about 5 times, each one about the length of a normal
shift.
I dropped it back to 3rd and drove about a mile and then back to OD. I drove another 7 miles in OD, part of it over 100mph and it didn't have trouble.

 

[Mark Nixon]

Crank sensor can also do this, I believe.

Mark.

 

[biggy238]

I thought about that on the way home and then forgot to post.
I relocated it when I deleted my fan hub.
I didn't notice the tach dropping any but I was busy cursing at the time.

I will check it out before I head home.

Thanks for the reply

 

[Kick Start]

Poor turbo

 

[biggy238]

The fuel is all the way back. Just wait.....