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Busy Busy
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Discussion Starter #1
I'm workin on a friends truck and here is the background.

2001 Manual.

New alternator put on a couple of weeks ago.
New Batteries yesterday.

Start the truck, runs great. Put a multi-meter on the batteries and you can watch the voltage slowly dwindle down from 11.8v or so. The truck will eventually shut off when it reaches 6.4v or so. If you turn the headlights on it will only go down faster.

If you put the positive lead on the back of the alternator it will read whatever the batteries are reading. If you unplug the alternators 3pin 2 wire connector it will drop .3v and continue to drop.

I put a known good alternator on the truck and it does the same thing.

I'm thinking it's a shorted wire somewhere from that plug back to the 42 pin connector or something not allowing the alternator to charge the batteries while running.

I probed #35 of the female side of the 42 pin connector and am getting .001-.003v.

Any thoughts short of replacing the entire wiring harness?


Here is a 2001 Truck 42 Pin Connector.

http://i103.photobucket.com/albums/m141/rpm-inc/alldata/Untitled.jpg
 

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Busy Busy
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Discussion Starter #2
This is with the known good alternator... it's the same with the new reman alternator.

12.44v with truck off.

Voltage idle - Time

11.97v idle @ 3:29pm
11.92v idle @ 3:31pm
11.87v idle @ 3:33pm
11.82v idle @ 3:35pm

= 1 hour and 48 minutes later this truck would die again.
 

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Busy Busy
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Discussion Starter #3
I probed #35 of the female side of the 42 pin connector and am getting .001-.003v.
Correction, I probed it and it ohm'd out to .1 and beeped when I put it on the audio setting (fluke multi-meter). This was for both sides of the alternator plug to the 42 pin connector on the driver side valve cover.

Looking for a pin-out diagram for the PCM now...

PS. the gauge on the dash reads and responds nicely to changes in voltage.
 

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Almost like something is getting hot and becoming more resistant. Check your grounds, might have a dirty one.
 

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Busy Busy
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Discussion Starter #5
Ohm's out to PCM plug.

Main power wire @ starter solenoid was loose, now tight...


Still dropping.
 

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Busy Busy
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Discussion Starter #6
Think I got it..... test driving it now.........
 

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Engine ground almost broken in two?
 

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WIth all the updates Marty, I dang sure hope you got it figured out lol.

You pretty much asked, discussed, and answered your own question Haha, but yeah what was it?
 

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WIth all the updates Marty, I dang sure hope you got it figured out lol.

You pretty much asked, discussed, and answered your own question Haha, but yeah what was it?
Sometimes, that's all you need, something or someone to bounce stuff off of. But yes Marty, fill us in. Hope your test drive didn't leave you stranded twenty miles from home.
 

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Busy Busy
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Discussion Starter #11
Good to go. PCM issue.
 

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Wow. Did you have to replace it?
 

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I was thinking the voltage regulator was in the pcm but not sure, if thats the case, probly new/different pcm
 
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