2004LB7 to 2006 LLY/LBZ Swap Questions

1FastBrick

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Dec 1, 2016
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Ok some of you may have seen the Vats thread I had earlier on a Swap truck I am trying to help someone local with. https://www.duramaxdiesels.com/forum/showthread.php?t=84165&highlight=LB7+LBZ+swap The swap Is running But I believe it has other electrical issues which is why I am starting a new thread.

Vehicle in Questions is a 2004 LB7 3500 dually crew cab truck. 2WD

Drivetrain swap 2006 LLY/LBZ 4WD. Yes, modified 2004 frame for front diff. Everything hooked up and functions.

Entire 2006 Dash harness with 4x4 push buttons swaped over with 2006 BCM and column from donor truck to the Project.

Everything seems to work and function for the most part. But there are some issues I don't know how to adress. I looked at it again yesterday And I believe everything is plugged in correctly.

1. When you turn the key on to the run position but do not start, It seems like only 1/2 the things are powering up and working. Cluster lights up, But no display or additional lights like the check engine light.

No Power to the windows or door locks.
The HVAC back lights come on but no Display or function.
No Radio function.

To me, It seems like this would be The BCM not waking up or receiving the signal. Or something along those lines.

After you start the vehicle and let it run, everything comes to life and works as should after a few seconds. Like maybe 5 seconds.

2. The Fuel gauge reads Empty even though its full.

My understanding is that the senders polarity are backwards or something along those lines between the 04 truck and the 06 cluster and that it just needs to be scaled in the tune. I however have not seen How to properly scale it. Still looking for that info if someone knows how to do it correctly.

Or does the sender need to be swapped out from the 06 truck?

Any help on this subject would be greatly appreciated.
 
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KyleC4

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Dec 30, 2016
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I’m going to have to look over the schematics but I do know that the ecm controls the check engine light. And it’s IPC logic that turns it on. I’ve had bad clusters as well that would take a few minutes to power up after starting vehicle.

But yes with the BCM being the power master on these trucks if it doesn’t send out signals of ignition position on class 2 line then the other modules have to wait until engine is running. That’s due to ecm sending signal on class 2 line.
 

1FastBrick

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I’m going to have to look over the schematics but I do know that the ecm controls the check engine light. And it’s IPC logic that turns it on. I’ve had bad clusters as well that would take a few minutes to power up after starting vehicle.

But yes with the BCM being the power master on these trucks if it doesn’t send out signals of ignition position on class 2 line then the other modules have to wait until engine is running. That’s due to ecm sending signal on class 2 line.
Thank you for chiming in.

I dont believe its a bad cluster.

I have No power to the Window switches, Door locks, Radio, Partial power On the HVAC controller and cluster (Only the back lights) When in the run position. I tried turn the engine off and key back on to the Run position and it kills the power again.

I am thinking either the BCM, Or the electronic portion of the key switch.

Also a possibility of a class 2 data wire or CAN wire broken somewhere. I know at least the ECU/TCU is CAN based In 2006 on the Duramax.

Since he used the entire dash harness, the Column, and BCM from the same 2006 donor, I would think it should be correct.

Only other thing I could think is if he maybe forgot to use the 2006 Fuse box But IF that where the case I think it would have other issues. Like things not powering on at all.
 
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1FastBrick

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If any one has any ideas or knows how to scale the fuel gauge in the LBZ ECU it would be much appreciated. I havent seen any actual details on how to do it in a swap like this.