Whatizit-wiring edition

This connector is on the harness that has the ESC 4-prong connector and the knock sensor terminal:



Long enough to reach the distributor, but I don't believe that is where it connects......

I’ll poke around my car after the rain stops to see if I can figure it out. It looks vaguely familiar, but I can’t tell you what that particular connector goes to off the top of my head.

1987 GMC Jimmy said:

I’ll poke around my car after the rain stops to see if I can figure it out. It looks vaguely familiar, but I can’t tell you what that particular connector goes to off the top of my head.

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Raining here too!

Looks like it would plug into distributor cap and pink power lead plug into it.
I can't imagine why..............
And, I can't find it on any schematic yet.
But, is part of ESC harness along with 4 prong dist. plug,knock sensor wire,2 prong "tip in" vacuum switch and ground wire.
I am hoping it not necessary.....

Are you talking about the one right above the distributor? I've always wanted to know what that was for too. I already have the tach and power wires in my distributor so I have no idea what it plugs into.

82sbshortbed said:

Are you talking about the one right above the distributor? I've always wanted to know what that was for too. I already have the tach and power wires in my distributor so I have no idea what it plugs into.

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Not it. Close,tho....
The harness comes out where you have a rubber plug just under your harness on the left side in the pic.

I believe that I have figured out that it originally connected to the distributor, and the 12v power wire plugs into it. This supplies the distributor and voltage to the ESC controller behind the glove box inside the dab.

My ESCs are controlled by ECM and module, not the pre-87 controller type deal. I’m still gonna look at the hot sheets, but let’s also get @hatzie and @chengny tagged here.

If that's the ESC power wire it'll route through a firewall grommet to the ESC controller along with the Knock sensor wire and the wires from the Weatherpak ESC connector from the distributor. There are a couple other wires as well.

If you buzz it out it'll be a pink wire in Terminal F on the ESC controller plug. F is in the centre right next to the key. On the automatic transmission trucks it's nestled between a Yellow and Light Green wire. The Manual Transmission trucks don't have the Yellow wire.

Download the 1984 wiring diagrams and page down to the ESC variant drawings in the centre panes of PDF page 13.

hatzie said:

If that's the ESC power wire it'll route through a firewall grommet to the ESC controller along with the Knock sensor wire and the wires from the Weatherpak ESC connector from the distributor. There are a couple other wires as well.

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Yessir. Also the wiring for the "tip in" vacuum switch.
Thank you.