I have a 1990 Dodge D150 and we had some problems with the window motor and stuff. We fixed all that and now I am getting error code 37; part throttle unlock(PTU) circuit, open or short detected. The battery died overnight I think because I left the hood up and the door not closed all the way. Dad insists it's alternator or something but we had the alternator checked and it came back good. I put a voltage meter on it and it read 12.4 with truck off, 12.1 when truck was on, 11.95 when lights turned on, then 12.4 when lights/truck turned off. Waiting for dad to get home so we can see what the voltage is on rev and I would love to take it out for a drive but my 240sx is dead behind it for the time being. I leave to move 600 miles away in a few days so I want to make sure the truck is dependable. It's been a good truck up til now and I think the battery just died because we left lights on. As the voltage, it's an old truck... Dad insists there is something wrong but we are completely lost on what it could be. I have no idea why the voltage would go back up to 12.4 when I turn it off. I've start/stopped and moved it back and fourth a little in the yard and this is always consistant. Any help would be greatly appreciated!

 

I idled for half an hour and my voltages went down 0.1v across the board. I read it could be the voltage regulator but I don't see one on the firewall anywhere :S

 

You should be seeing at LEAST 13 volts, even at idle.
Voltage regulator is in the PCM......

 

We put an external voltage regulator but the volts stayed the same. We replaced the alternator and we are only getting 12v from the back of the alternator...

 

You have a wiring issue somewhere....

 

One of the things that is still getting me is I can't get voltage out of a new alternator. I unplugged the VR I just installed, turned truck on and took voltage with negative on the negative battery terminal and the positive ont he back post of the alt and it read 12.2 this morning and after an hour of idling and checking its now reading 11.4v at the alternator. I don't understand why the alt isn't putting out juice...

 

Because the regulator isn't telling it to...... Do you get output voltage with the external regulator hooked up? Is it hooked up right??

 

Full field the alternator to see if it's working. What type of regulator did you put in it? You should have checked that the one in the pcm is not working before doing so. Is the bottom diagram how you have it wired?
http://www.mopar1.us/charge.html