Tracing Firewall Wire(s)?

[LS1GMCTruck]

Example: I'm trying to figure out, which of the many dark green wires, coming out of my main firewall bundle(C-100 connector?) is the speedometer wire. According to my wiring schematic, it is a dark green. Trying to trace it, so I can hook it up to my VSS wire on the LS1 harness. Trial & error?, or is there a better way? Thanks, Gar

[RedHeartbeat]

remind us what year harness you speaking about

[LS1GMCTruck]

RedHeartBeat... Oops, It's a 1996 GMC C-1500...had a 4.3 Vortec/4L60E in it originally. Thanks, Gar

[1BADC10]

I noticed that the Haynes/Chiltons manuals have gotten lazy about showing pinouts off the fuse block. I guess it is too much effort to do with a more clustered wiring than the simplistic 73 - 87 models.

[Chuck21387]

<div class='quotetop'>QUOTE(LS1GMCTruck &#064; Sep 24 2006, 01&#58;43 PM) [snapback]66321[/snapback]</div>

RedHeartBeat... Oops, It&#39;s a 1996 GMC C-1500...had a 4.3 Vortec/4L60E in it originally. Thanks, Gar
[/b]

Excuse my ignorance, but didn&#39;t the old 4L60E have a VSS? can&#39;t you use that wire? or shouldn&#39;t the plugs be the same?

[LS1GMCTruck]

Yes, I believe the original 4L60E did also have a VSS, but was also part of the original V-6 engine/tranny wiring harness. This harness was hardwired to the computer and main firewall group of wires, that have since been cut, to separate/remove them from the engine compartment. There were quite a few wire feeds like this, that were not just a simple male/female plug together connection. I guess, I&#39;m just wondering if there is a way to "test" the speedometers dark green wire, coming out of the firewall, to indicate whether or not it is indeed, the speedo wire? GM trucks, beginning in 1996, are a bit more involved in the wiring, than all previous years. Thanks, Gar

[1BADC10]

I would imagine you could send low pulse voltages to the speedo. <---not a pro, but just a thought.

[LS1GMCTruck]

<div class='quotetop'>QUOTE(1BADC10 &#064; Sep 25 2006, 05&#58;57 AM) [snapback]66434[/snapback]</div>

I would imagine you could send low pulse voltages to the speedo. <---not a pro, but just a thought.
[/b]

O.K., I&#39;ll bite. I could try that I suppose. Where would I get/source these "low pulse voltages" from? Thanks, Gar

[1BADC10]

<div class='quotetop'>QUOTE(LS1GMCTruck &#064; Sep 26 2006, 03&#58;07 PM) [snapback]66692[/snapback]</div>

O.K., I&#39;ll bite. I could try that I suppose. Where would I get/source these "low pulse voltages" from? Thanks, Gar
[/b]

Arghhh.... brain fart. Gotta research. Wondering about voltage or ampres pulses. Will have to look into. N E 1 else have insight on this?

[98hd]

You can go on alldata.com and pay the 25 bucks for the membership and it will get you access to all the wiring diagrams. I just did that to go through my engine harness and pull all the now unnecessary wires out.