This problem is starting to become more frequent. In the morning when the truck is cold, the Gen light will come on and the truck will not charge. I'm also losing 3,4 shift and od, after about 20 min sometimes less everything will return and the truck will function normally. What are some possible causes of this.

 

To get some answers or good ones , you need to put your truck description / fill in signature from the user control panel .
You could start with checking alternator , wiring to & from alt. & batteries , then check out the crank sensor .
Give some history , how old are the batteries , alt. ?

 

Truck is a 97 12v auto, alternator, crank sensor and pcm are new

 

Considering what you've already replaced the most likely problem is the hardest to find, a bad connection.
Most likely right at the PCM.
My bet is the parts that were replaced have nothing wrong with them.

 

RKS, when you have this problem, do you also lose your Tach?

 

could be a bad ground.

 

Look on your left battery positive post. You will see a big wire going to the starter, another going to the other battery. You will see a slightly smaller one going to the fuse box behind the battery. I bet this wire has a bad connection. It feeds almost everything on the truck including the alternator.

One test you can do is cycle the key switch on,off, on, off, on quickly and read the codes. You may see a 12 or a 55 but these are not important. You want the ones between the 12 and 55. I bet you will see a code 46 or 47. 46 is batt voltage too high and you will see that because of the bad connection in that cable. The power or voltage is not getting to the battery. A meter will show you too.

 

I'm not losing the tach, just everything else and i'm gonna check the battery connections today.

 

I'd try replacing all the battery cables. Positive and ground.

 

Could it be the tps going bad?

 

I have never seen or heard of it doing all you described, but if I remember correctly the TPS gets its 5V from the same source the ESS does.

You would think if the TPS was causing you to lose 5V to the PCM you would also lose your Tach though.

I would look elsewhere. Perhaps one of the connections that were recently fixed?

 

I'm checking those now, could it also be the trans temp sensor, it only does it in the morning or at night when the truck has been sitting for several hours. Once it stops during the day I dont have any problems

 

make sure you check the ground at the front of the engine (pcm ground) and check the main power feed at the bat to fuse block

 

Could bad batteries be causing this problem?

 

There is no reason the TPS or tranny temp sensor would make the Gen light come on or affect charging.

Check each female pin at the PCM connector carefully one by one.
The connectors are cheap, break apart or get elongated easily causing bad connections.