The battery temp sensor is the round 'cut out' under the battery, looks like it's a part of the battery tray. Do a search on the boards to figure out what it's for--I can't remember. I hate to stab in the dark and spend $150 to have my PCM rebuilt... then find out that my alternator might have bit the dust. I've had it tested twice--both times the alt tested good. However, it is old and I don't know when it was last replaced. I might try the alt (~$115) first simply because it's local.

Are there any other symptoms of a bad PCM?

 

that's what i would do too, if it were my truck.

 

Problem with trying a new ALT is you'll have to pay quite a bit more without the turning the old one it, and you don't want to turn in the old one without first being sure its bad ,,, But so long as you are sure you can take it back and get a refund, shouldn't be a problem, just keep the old one and pay more.
If it fixes your problem, the old one can be taken in and you can get your $50+ core charge.
I wouldn't tell them your exact situation, they may not take it back if they know it has been installed and used, if only for minutes.

Maybe try taking it to an Oreilys, they have a bad ***, state of the art bench tester there.
If it tells you its good, its good - Then you can be nearly positive its the computer.

The voltage regulation function can go out, and everything else works fine.
I know, because it happened to me, took the ALT out multiple times to have it bench tested ect.
I had a pro with a $10,000 scan tool diagnose it, he told me it was the computer, and he was right. Swapped the computer half a year ago, been a steady 14v since then.

I, and alot of other guys, get them from these guys ,,, You can get your $$ back if it doesn't fix the problem, have a lifetime guarentee, they are simple to install, just a matter of 3 harnesses and a few bolts - Be sure to disconnect that battery before the swap.

http://tinyurl.com/yc6po3a

 

Okay, took the *blind* plunge and switched the alternator. I've been driving it for 24 hours with no problems. It appears that the problem is solved.

I did have the old one bench tested AGAIN (3rd time) before buying the new one. Again, it tested good. So chalk one up to bench testers sometimes being wrong.

For the record I have a 1997 Dodge Ram with a 2000 5.2L engine. The old alternator was a NipponDenso 90A. The one I purchased was a rebuilt DuraCrap 90A alternator. In AutoZone's computer they didn't have the 90A for the 2000 5.2L, so I assume my old alternator is at least 130k miles old (the engine was switched 130k miles ago). Only one difference between the old and new--the pulley size. The new pulley is about 30% larger. Still, had no problem fitting the belt back on with the automatic tensioner.

 

sounds like gremlins, not trolls lol

 

Good for you man! Keep your volt meter close to you to check it once in a while.