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What wire for the Speedo?

3K views 19 replies 5 participants last post by  Theo's 
#1 ·
I have a 2005 Northstar 4.6 from a Deville I believe in a kit car. I want to hook up a speedometer and need to know which wire to conect into and were would be the best spot. I also Believe I'm using a Pontiac GXP ECM. My speedo is calibrated for a GM 18 pulse sender. Can anyone help with this?

Also my new radio with navigation is asking to be hooked up to the speed sensor wire. can I use the same wire?

Why would the radio also want to hooked up to the back up lights and parking brake?

Thank you for any help or advice!!!!

 
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#5 ·
Hmm, you're going to have to ID the trans for me. Behine the engine, farthest away as you look at your pic above, is the transmission. On the top of it as u look thru the hood, about 5inches behind engine, is a stamp that will say 4T80E, or possibly another identifier. you may have to lift a wire harness or take off your air induction stuff, or both... to see it.

So is that the radiator smashed against the engine (or almost at least) in right side of pic above? WOW is that close.
 
#14 ·
Also my new radio with navigation is asking to be hooked up to the speed sensor wire. can I use the same wire?

Why would the radio also want to hooked up to the back up lights and parking brake?
If the unit also plays videos or has video input, it could use these signals to prevent you from watching a movie while driving, or to switch to video input from a backup camera if available.
 
#16 ·
I really aprciate the help so far!!! But... I have chased for wires that I believe may be gone out of my harness but who knows:bonkers:. I did find the Vehicle Speed Sensor with the purple & Yellow wires coming off it. Then I read this on Autometers website:

"Most factory equipped speed sensors will operate our speedometer. If you are running a late model transmission in an early vehicle with no computer, then that is o.k. You will have two wires on most factory speed sensors. Ground the low-side signal wire and run the hi-side signal wire to the speedometer and calibrate. It’s just that easy. "

I do not know if the yellow and Purple wires are still doing anything for the ECM. Should I do as it says and ground the Low- Side and use the hi- side, should I just try and use the high side? My biggest fear is hurting the ECM.

Thanks for any input!!!!:bouncy:
 
#17 ·
I would think you would still need to run the speed sensor through the PCM otherwise it will set a DTC. PIN 8 on C1 of the PCM goes to the dash wiring through a large connector that is usually mounted on the driver side strut tower (in normal caddies). It should be a dark green/white striped wire.
 
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