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2007 Chevy Silverado, 5V Reference nightmare. Paul you gotta see this one

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09 Oct 2019 10:22 #34112 by rpd1125
Okay guys here is a crazy one. 2007 Chevy silverado. Truck came in with harness cut all over the place and nothing powered on. after a few hours of restoring power to all circuits and Reprograming a used computer per customers request. The Truck will only crank over the first time you tryu to start and then it wont after that.

The PCM will no longer power the starter relay or coils.

If you let it sit for 5 mins or so it will try to start again but only with on first crank after that it wont even crank over.

We are getting ready to plug and program a brand new PCM but want some input on this one. As you can see on this diagram, this is the 5V reference diagram from PCM to various ciruits. as you can see 5v-1 has voltages all over the place but not exactly 5V the other 5V-2 is perfect. all sensors on the 5V-1 have been disconnected and I have checked all of those 5V reference circuits for shorts to ground and non found.

Please any input would be appreciated. Previous repair facility hacked this thing all over the place.

Initial customer concern was it was lacking power and they started throwing parts at it and now its been brought to me piece it together. Ive had truck here for a few days. Customer is at his spending limit with the purchase of a new pCM.

hope you guys can shed some light. Im not sure what else to check'
'
The PCM has solid Power and Grounds. And its recieving Crank Request from BCM every single time we try with the key but its not powering the starter relay or firing anything. It will only attempt to start on first crank.
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09 Oct 2019 10:23 #34113 by rpd1125
Here is the diagram inserted to thread
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09 Oct 2019 17:15 #34123 by Cheryl
Only other thing I’d do is check the 5 volt reference wires for high resistance. Load test the wires other than that you said powers grounds are good id put a new pcm in it. Also check pcm terminal fitment

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09 Oct 2019 17:32 #34124 by rpd1125
Already did that. circuits are clean

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09 Oct 2019 17:37 #34125 by Cheryl
Sounds like a new pcm will fix it

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09 Oct 2019 18:23 #34127 by rpd1125
Tried a used PCM supplied by the customer and we have restored the 5V reference to all circuits, Now we have Theft Deterent Module code saying its in learning mode. Going to have the TDM Reprogrammed and the key reprogrammed

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