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Old 07-17-2020, 09:11 AM   #5
TrybalRage
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Join Date: Jun 2014
Location: Reading, PA
Posts: 203
Re: Lm7 swap harness question

Quote:
Originally Posted by FoxJ12 View Post
I am in the process of pulling an LM7 from an 02 Avalanche and need some help. The engine is out with the tranny and I have labeled the plugs and have the harness draped over the left wheel. I want to continue to pull the rest of the harness and later attempt to build my own stand alone, but I am not sure of exactly what all I need. There are a boatload of wires and I hate making more work than I need to. I can see where the main bundle exits the firewall and enters the engine bay fuse panel. This is where I am blocked. Do I pull from under the dash or separate things here? What pieces need to come out from under the dash? If any?

Plans for the truck in case they’re needed:
70 c10 shortbox
5.3-4l60e
A/C
NO power windows, locks, etc.
Possibly an external fuel pump and 100% relocated tank.
Tach, oil, fuel, (digital?/analog?)speedo gauges, maybe vac gauge.
Run the cats and O2 sensors? Not sure here...
Install the obd2?
Very stock looking but with some get up and go.

Thanks for the insight. I feel like I’ve jumped in the deep end with no idea how to swim.
You shouldn't need anything but the engine harness to the fuse box. Some people choose to keep the box, but most don't. Is this a drive by wire motor or drive by cable? If wire, then you want to grab the pedal and harness/tac module as well.

Yes, you want the pre-cat 02's as the engine needs them to run properly. As far as having cats/post 02's, that's personal preference and local laws. I'm planning on adding cats but NOT the rear 02's.

Yes, you want to add an obd2. You can probably yank that off the donor and just cut the wires, then wire it back in manually on the C10. You'll need it for tuning or even just diagnostics, or if you want to add something like dakota digital gauges they offer an OBD connection option.

I've found the 'ls swapped square body' c10 group on facebook to be immensely helpful. Even if you're not in a square, there's tons of good info there on wiring, setup, etc. There are probably some other groups as well more specific to your truck. Another great resource would be ls1tech.com, they have a 'swaps and conversions' section.
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1985 C10 Silverado LWB LS Swapped! Other Stuff

2010 Suburban 2500 LT 4WD
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