Need help hooking up my Classic Instruments speedo to VSS...

[Travis Talbot]

I'm trying to install my speedo from Classic Instruments and I'm a little confused on the VSS signal that need to go to the SN77 Speedometer Signal Interface. It appears that I need two wires for the VSS going to the SN77 Interface; sensor ground wire and input wire (VSS signal). Here's my problem, I'm trying to tap into the VSS wire (pin 68) off my PCM. It's only one wire and the SN77 Interface needs a VSS ground. Does anyone know how to wire up the SN77 Speedo Interface? Any info would be greatly appreciated ...travis

[Travis Talbot]

I thought I would post this to see if it helps...

From instructions...
"If using the SN77 speed signal interface:
Connect one wire of the transmission VSS to the SN77 signal ground and the other wire of the transmission VSS to the SN77 input."

[Tim Potts]

Travis, When I installed Classics in my Roadster they didn't have that innerface. Anyway you have two wires from the vss/oss sensor a DG/WH CIRCUIT#970 which would be your signal wire and a GY/RD CIRCUIT#359 which will be your signal return wire this #359GY/RD SIG RTN is the same circuit that also runs to your engine sensors.
#970 would go to your "input/high" and #359 to the "sensor ground/low input".

Also if you are going to tap into the speed/cruise control connector pin #68 WH/OG circuit#239 this would be the same as tapping into pin#84 of the PCM circuit #970. Pin #91 at the PCM is your SIG RTN. Just wanted to make sure that you realized that in your diagram above that what you thought was a pin of the PCM was indeed a pin of the cruise module not that there's a problem with going there.
Tim

[Travis Talbot]

Tim,

Thanks so much for your post. It looks like it's exactly what I need. I was getting hung up on the instructions from Classic Instruments using the VSS signal, I wasn't even considering the OSS (Output Shaft Speed) sensor.

I removed the images of the VSS diagram above so that it wouldn't confuse others reading this post and replaced them with the OSS diagram images below.

[Paul Westerbeck]

Tap into the wire going to pin 68 of the computer. run that to the input of the sn77. See the instructions below. You need to connect it like option 1 (ECM Signal) on page 13.
http://www.classicinstruments.com/Us...n%20032708.pdf