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2008 Chevy Silverado 1500 4.3 W/T

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30 Jun 2020 14:32 #40995 by Matt T
Replied by Matt T on topic 2008 Chevy Silverado 1500 4.3 W/T

Chad wrote: Cheryl is NOT suggesting to short CAN+ to CAN-. But to maintain bus continuity, like this:


Oh so the can bus runs thru' each module instead of just to it. Makes sense now. Well at least having to jump hi to hi and low to low makes sense. Having 4 potential network failure points on most of the modules makes no sense whatsoever...

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02 Jul 2020 23:23 #41055 by NuckingFutsKustoms
Replied by NuckingFutsKustoms on topic 2008 Chevy Silverado 1500 4.3 W/T
Ok Im back, here is where I am at. Have coms to ECM TCM and most of BCM. What I dont have coms to is my IPC , Radio, or Door locks from scanner, the locks work from the door switch though.

So I figured I would just start at what doesnt work and work on one thing at a time so I started at the Ignition switch, What I have there is 3.9 v on the white wire which If Im seeing it correctly is the 5v ref. and Im seeing 3.9v on the pink wire witch again if reading it correctly in my signal to IGN of BCM. thats in RUN postion btw, turn the key to start and I get 2.5v on white wire and 4.1v on pink. Now when I unplug the switch altogether I get 4.9v on white and 0 on pink. Since Im brain dead at this point in time that seemed weird to me so maybe just maybe it was my switch bad. I know they said they replaced it but how do I really know this. I just happen to have a new one there so changed it out right quick and still had the same thing. SO I guess its supposed to be like that??? Tommorow I suppose Ill do some origami stuff and fold my way up under the dash and back probe the BCM and see if I get the same things. Unless yall give me another direction that Im not seeing.

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03 Jul 2020 13:56 - 03 Jul 2020 13:56 #41065 by Chad
Replied by Chad on topic 2008 Chevy Silverado 1500 4.3 W/T

that seemed weird to me


:blink: Seems weird to me, too.



This is Copy & Pasted from Alldata:

Circuit Description (Key Start)

When the ignition switch is placed in the Start position, a discrete 12-volt signal is supplied to the body control module (BCM) notifying it that the ignition is in the Start position. The BCM then sends a message to the engine control module (ECM) notifying it that CRANK has been requested. The ECM verifies that the transmission is in Park or Neutral. If it is, the ECM then supplies 12 volts to the control circuit of the crank relay. When this occurs, battery positive voltage is supplied through the switch side of the crank relay to the S terminal of the starter solenoid.

Not much help.

"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer."
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03 Jul 2020 14:15 - 03 Jul 2020 14:43 #41066 by NuckingFutsKustoms
Replied by NuckingFutsKustoms on topic 2008 Chevy Silverado 1500 4.3 W/T
So I need to check my 12v feed and my grounds and work my way back then?
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03 Jul 2020 23:19 #41071 by Hardtopdr2
Replied by Hardtopdr2 on topic 2008 Chevy Silverado 1500 4.3 W/T
According to the schematic white is 5v reference and pink is switch position signal for start position. So with connector disconnected those readings look ok. But the low voltage in run/acc is on white concerning but there are two pinks in the diagram you posted so I would check which pink wire you checked to make sure you read the correct one. I would check voltage at the 2 amp fuse to see what you have for supply voltage after that.

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04 Jul 2020 03:30 #41078 by NuckingFutsKustoms
Replied by NuckingFutsKustoms on topic 2008 Chevy Silverado 1500 4.3 W/T
Yeah the diagram shows 2 pinks but I only have one pink in my connector.

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