wiring questions 5.3 into 99 hoe

[tommypvt]

Was going to 0411 swap my 99 Tahoe then do a 5.3 down the road. Now have the ability to pick up a complete 2003 5.3 truck with low miles so changing plans.

Been reading through the swap threads and have a bunch of questions on integrating the ls pcm into the 99 tahoe.

I know I can just repin what I need out of the 99 harness and add it to the ls harness. My big questions are do I keep the 99 underhood fuse relay block? or do I swap the new 03 one in?

Is there any real comprehensive threads for this wiring swap. I seem like I am spending a lot of time reading generic, incomplete or info from different types of installs. If someone can point me in the right direction it would be awesome.

 

[Cokeman95]

http://www.lt1swap.com/wiringharness.htm

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[GMRedline]

This question gets asked a lot. Unfortunately there is no step ny step guide to doing this. There is a lot of information out there for people who have the ability to learn what they read and apply it.

This is a good thread on this forum.

http://www.gmt400.com/threads/my-ls-swap-in-2-dr-2-wd-tahoe.28889/

It would be awesome if someone would take the time to write a step by step tutorial of the swap. 96+ LS swaps are basically the same.

 

[GMRedline]

This question gets asked a lot. Unfortunately there is no step ny step guide to doing this. There is a lot of information out there for people who have the ability to learn what they read and apply it.

This is a good thread on this forum.

http://www.gmt400.com/threads/my-ls-swap-in-2-dr-2-wd-tahoe.28889/

It would be awesome if someone would take the time to write a step by step tutorial of the swap. 96+ LS swaps are basically the same.

 

[tommypvt]

So purchased my donor vehicle a 2003 silverado and started in on my engine swap.

Pulled the lm7 harness. It's a very straightforward almost standalone engine harness. Looked at lt1swap and and just went through and labeled everything. Pulled all the wires out of the c2 connector and labeled them instead of cutting them off. I dont think i am going to weed all that much out of the 5.3 harness as he did.

Starting in on my yukon now and what a difference. The heater blower motor is part of the big bundle that runs across the engine and is mixed in with all of the motor wiring. I am going to try to separate that out along with anything else that needs to stay. I think i will pull the 5.7 now after removing just the wires that are connected to it. That way i will be able to get in the engine bay and work on the harness leaving the tranny and everything past the engine connected. I am going to try to separate out what i need to keep and what i can toss.

I want to keep the ac wiring which gets tossed in the lt1swap stand alone facebook directions.

My goal is to keep the tahoe underhood fusebox and just feed power from that to what I need instead of trying to run a separate fuse box and relays since all of what i need is already there. I just need to match up wiring.

Should be a chore. I will try to get photos of what I am doing. The gmt400 wiring is not nearly as compartmetalized as the 5.3 and it will take some work to sort.

 

[tommypvt]

Worked on the 5.3 harness today. Left the C-100 connector on the harness and cut the plug out of the donor truck.

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This will work pretty well The C100 has the MIL VSS Tach OBD Data on it. It also has an AC wire and cruise control wiring.

I chopped the white tach feed off the yukon coil plug and pulled it through the tahoe harness to get it by the ecu.

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Most of the other wires are on the blackbox black pcm connector. I pulled the pins for MIL OBD Speedo etc and will solder it to the c100 plug.

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The purple starter solinoid wire I will connect to the yukon underhood fuse box . I am going to try to use the original fuse box as much as possible but it may be easier right now to just run a small fuse block for all the 12v keyed power.

 

[tommypvt]

Got the 5.7 out of the tahoe this weekend and started weeding the tahoe harness.

I disconnected the plugs under the brake booster which ran to the smaller harness in the engine bay. This harness ran to the transfer case and i think the rear o2 sensors. It also ran to the VSS.

I had already swapped to a np241 so there were a bunch of unused transfer case plugs. There were a couple connectors that connected this smaller harness to the larger main engine harness. I just disconnected them and pulled the whole thing. I separated out the vss and when i unwraped it found a small female to female connector. This plugs right into the 5.3 harness VSS connector. So that makes extending the VSS plug easy. My donor truck already had the tranny and tcase pulled so I am not sure if this little VSS connector is part of the 5.3 harness.

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Not having the 246 in it will make the wiring a bit easier since I would have had to keep that entire harness in for the transfer case plugs.

The tranny range plugs were cut off the 5.3 harness. Didnt realize why untill i tried to get them out of the tranny and they were impossible to get undone.

So next step is to weed out the main engibe harness and try to remove as many of the old plugs as possible.

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This branch going to the tranny is just the main plug. So tommorow i am going to pull it and then try to separate out what i dont need.

 

[GMRedline]

That looks like a mess. It took me a while to figure out a standard automotive relay...

 

[tommypvt]

That looks like a mess. It took me a while to figure out a standard automotive relay...

Yeah me too. But now look at me lol. The fun part is not knowing what isn't working until its all back together. But I guess I will deal with that as the time comes. the last FI swap I did I missed a ground and burned up a couple MAFs before figuring out where it was missing. Good times. Even more fun when it doesn't manifest itself anywhere near the problem.

I should be able to sort this pretty well though after all this is done. I am sure other people have done this work. You were right in saying the information is out there. Just putting it in one location I think will help some people. I was searching all over for the tahoe bulkhead wiring diagrams and found them at LT1 swap.com. I will try to start a new thread and condense everything or put it in the stickie 96-99 swap. No reason for people to have to search for it all over the place.

 

[tommypvt]

Tackled more of the wiring last night. I just started sparating the harness and pulling everything that wasnt running through a bulkhead connector or attached to the underhood fuse box.

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Got pretty much everything separated out into a manageable chunk. The big ball of wiring is whats left of the engine and tranny loom. It will just be tossed. I cut out what was running from the passenger side bulkhead and labeled the wires.

I then pulled the drivers side bulkhead connector and started tracing wires from there.

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This is what I ended up with when I pulled the bulkhead connector. There are connectors to the fuel pump, fuel gauge and ABS in this mess. I started weeding this a bit more. I removed the ABS wiring since I am going to a solid front axle at some point.

Then the fuel gauge wiring fell on the floor. I didnt realize it was run through the computer on the 99. I have an email in to lexitech to see if my 03 computer can run it. I believe it can. I will have to add a pin to it though.

I am glad I didnt cut off the connectors from the 03 harness because on the white C152 everything is there to run the fuel gauge. So I wired in the tahoe fuel guage and fuel tank pressure plug (C130) into that.

Now I just have to sort the relays on the underhood fuse panel. Shouldnt be all that hard. You can see them in the top of the picture. Getting there.