91 c1500 wiring question

[gonefishin]

Anyone know what this box is or where this wire goes? Truck is originally a 4.3 v6 rcsb. The gray box has 3 purple wires going to it and is located behind glove box.

So long story short, truck has been apart for over 10 years and I’m just about finished with the ls swap. And I’m cleaning up the wiring. I don’t know where this plug goes. 1 end goes to the abs module, 1 goes up into the dash, and the other wire is this plug from under the hood.

I believe it is a brake switch diode or something like that from reading online. None of my manuals show it on the wiring diagrams.

 

[dyeager535]

http://www.mediafire.com/download/vu6y2ryij29i96r/1991_ST-375-91-EDD_Chevrolet_CK_Wiring_Manual.pdf

Hopefully that link works. Pdf page 72, RWAL diode.

Can't find the single connector brown wire, but this is tough on a phone. I see reference to a brown wire being the AIR solenoid. It's definitely not the EST bypass (timing) wire.

If the above link doesn't work, this is the site that the link is from. http://67-72chevytrucks.com/vboard/showthread.php?t=700011

 

[gonefishin]

Thank you that is exactly what I was needing!!!!! I’m going to print the whole thing when i get to work next week.

That wire i was holding is purple, but dirty so it looked brown.

So of the 3 purple wires 1 goes to the brake switch, 1 to the rear anti lock brake module, and the one i have been trying to figure out is for 4wd models. I even found the exact plug pictured. I guess it was never used because truck is a 2wd. I took the truck apart 10 years ago and don’t remember anything about that plug.
Thanks again

 

[dyeager535]

Thank you that is exactly what I was needing!!!!! I’m going to print the whole thing when i get to work next week.

That wire i was holding is purple, but dirty so it looked brown.

So of the 3 purple wires 1 goes to the brake switch, 1 to the rear anti lock brake module, and the one i have been trying to figure out is for 4wd models. I even found the exact plug pictured. I guess it was never used because truck is a 2wd. I took the truck apart 10 years ago and don’t remember anything about that plug.
Thanks again

Anything but factory wiring diagrams (heck, any manual) are usually garbage IMO.

Glad I could help.

 

[gonefishin]

Yea that’s totally true. I have an actual Gm service manual for my k5. I always wanted to get one for my 91. I’m going to print that one you sent me on 11x17 paper at work.
Thanks again

 

[Truckman4life]

1973-87(91) Factory GM Pickup Manuals

1973-87(91) Factory GM Pickup Manuals

forum.73-87chevytrucks.com

https://www.gmt400.com/threads/88-95-service-manuals.43575/ not sure if these ones work, my work computer firewalls may just be blocking the manual links in the thread.