won't lock into 4low

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BoominSVX

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OK, I found something interesting while playing around with the grounds on the truck. It gave me hope, but now I'm even more confused than before. The truck has run fine since I swapped the engine back when I got it. Aside from the service 4wd light, no real issues. When I started fishing for wires behind the passenger head, I fund one that I had forgotten when I did the engine swap. It comes out of the engine harness and marked blue in the picture. The issue I have is that now I don't know what it was for. This diagram doesn't tell me and I can't find any info about it. I have searched, but the LSX guys have overtaken the internet and sorting through all the irrelevant search results is killing my eyes. Also, What I cannot find is the ground listed in this diagram as G110 (drawn in red). There are two connections. One is the Ground Strap going to the body, the other is the wire I marked in blue. What does the blue one do, and can anyone tell me if a 98/99 escalade/tahoe/yukon has 2 wires to this bolt or 3?

What is the Blue one?
Should I have the Red one?
Why is my picture so small after upload??
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BoominSVX

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Okay, so nobody responded, but that doesn't mean someone else won't have this problem one day and I know what my issue was so I'm going to share. After another encoder motor, a TCCM, and a switch, I started testing wires which I usually never have to do. The orange wire had 12v as necessary, but when I jumped from pin E1 on the C1 connector at the Transfer Case Control Module to the same Tan wire located at pin D on the encoder motor pigtail, I had no contact. After hunting through the harness for a bit, I found that the wires run across the top of the engine. There's a larger main harness and a smaller harness running right along side it. Clips actually stick it right on the the larger harness. When I began searching for the tan wire in that harness, I found that 3 wires had actually melted through and broke from heat and contact on the rear of the driver's side valve cover. I never thought they got that hot, but I guess they do. After fixing my broken tan wire and the two others that had also suffered the same fate, all is well. Yep. I'm an idiot, but that wire runs all through Guam and back. I couldn't follow it. I only went to the engine harness because it showed p100 (grommet) through the firewall in the schematic. I knew they had to be in there. Check that your valve cover hasn't burned through the harness if things have gone crazy. All this was for C0323 and no 4Lo.
 

1999bigburb

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I dont know if this will help anyone or has been mentioned before regarding the 4 low not engaging issue with the electronic transfer case but give this a try...
Start the engine and when running place the trans in neutral as though you are going to engage 4 low. At this point shut the vehicle off while leaving the trans in neutral, of course hold your brakes if needed. After a few seconds start the engine again and IMMEDIATELY press your 4 low button. It will engage as it should providing all the parts are in working order. Do the exact same to disengage. I went through everything on my truck trying to get 4 low to engage until I stumbled across this, been working flawlessly since so long as I follow the procedure above. Still won't engage otherwise.
All that I think is happening is that I am sending the command to engage the 4low before the computer/electronics figures out there is some issue somewhere, by the time it does its to late...its engaged. I have helped a buddy with this same concern and he was super happy...he had no 4 low for 4 years lol. I can take a video if someone needs me to show them but really it's super simple.
 

GMRedline

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^^^^^ Interesting. I haven't been able to get mine into 4 Lo since I owned it. I should give this a try.
 

1999bigburb

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^^^^^ Interesting. I haven't been able to get mine into 4 Lo since I owned it. I should give this a try.

Let me know how it woks out for you. Just last night we went to meet some friends travelling/camping near our home...they had another friend travelling with them that had a 97 Tahoe with no 4 low...until last night. Hasnt worked for 7 years and now does. He couldnt believe it actually works for him now. I have a feeling that this may be an issue that has a simple "fix" for many folks with no 4lo.

If it works for anyone else let me know.
 
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