Does anyone have a electrical schematic for a 99 PCM? I'm trying to repair one and need some help.

Adam

 

I've tried, they call it a trade secret.

 

I was told that is in the factory service manual. Anyone have one?

Adam

 

You were told incorrectly. The manual has a section showing all of the connections to the PCM, but not the internal circuitry of the pcm itself.

 

I'm sorry. That's what I need, which wire in the connections do what and where they are located. Sorry for the confusion.



Adam

 

I have factory manuals for a 2000, they should be the same or close. Ask specific questions and I will look them up for you.

 

Here is a question for ya, My altenator went out this morning and after I put the ew one on it won't charge, there is no juice getting to the altenator from the computer. Now is that from the ECM or the PCM and if so where is the wire or can it be fixed. thanks, Dean

 

It is not fixable, but you do not have to replace the PCM. Just tape off the field wires that go to the alternator and add an older model regulator. They are about $7.00 at the parts store. There is a schematic on the board for doing that. It is a perminate fix.

 

So basically, unhook the plastic plug on the alt. get a voltage regulator, run a wire from the ASD to the regulator then on to one of the small terminals on the back of the alt. Then run a wire from the other post on the ALT. to the other post on the reg. then a ground to the REG from the ALT. one question, where is the ASD located. Thanks

 

The ASD output is a number 10 wire and is green with an orange stripe on a '99. It can be found on the wiring of the power box on the drivers side, where the relays are or it is pin 12 on plug C3 on the PCM on the passenger side. This wire has the same sequence of on and off as the fuel pump and is the feed that the PCM uses for both the fuel pump and the alternator. You are just jumping ahead of the PCM when using this wire for the feed.

If you hook the two wires on the regulator backwards and feed 12 volts to the wrong pin, you will scrap the regulator. It will not hurt anything else, just reverse them and it will work. Does not matter which alternator pins are fed to which pins on the regulator.

Be sure to do one thing though, do not leave the PCM wires connected while using the regulator, it will not work that way. They must be disconnected at the alternator.

 

This regulator mod will not set any codes or affect the truck in any way other than control the alternator. The temperature sensor for the battery under the drivers side battery will no longer function. The only thing that will be noticed is that in the winter the charge rate will be higher and lower when it is warm outside. This is normal.

 

 

Great picture Bill, thanks. It answers two pages of talk.

 

Thanks, guys. I found that pic this morning, right now I am waiting on the pigtail for the regulator. It should be here in half an hour I hope. As long as the color is the same on a 2000 I found the wire over by the pcm and will splice into it there. Thanks again. Dean

 

well I hooked it up and when I did it blew the engine control fuse, when I replaced the fuse I unhooked the wire from the ASD wire on the pcm, It had power through it with the key on but when I started the truck and hooked it back up it blew the fuse again. Maybe I am doing something wrong here but I don't know what it is