1990 obs speedo connection

[exboatracer]

I have searched a bunch and can't find out what color wire (s) need to be hooked up from the inst cluster to make the speedo/odometer/trip to work. This is the last piece of the puzzle so if anyboby out there got their 1990 speedo working I'd love to know how. I have a designated wire coming from my pcm thats labeled speedo and it needs a home!! Thanks.

[farmtruc]

You could pull the cluster apart. Comes apart easy enough if i remember correctly; Follow the ol skool circuit board trace and temporarily make a connection.
Or just wait until someone replies lol.
I used to know but forget after inhaling too much race fuel.

[hotrod]

I have searched a bunch and can't find out what color wire (s) need to be hooked up from the inst cluster to make the speedo/odometer/trip to work. This is the last piece of the puzzle so if anyboby out there got their 1990 speedo working I'd love to know how. I have a designated wire coming from my pcm thats labeled speedo and it needs a home!! Thanks.

here's a quote from my thread that chevy-art told me

For the speedometer to work I used the wires what come from the VSS on the transmission, they disconnect from the rear of the trans and go into the cab. The colors are HI 400 Yellow and LOW 401 Purple.

maybe this will help you

[exboatracer]

I found those yellow & purple wires(also a ppl/wht wire). I even labeled them "old trans wires" and capped them off & tucked them in my harness coming from c-100. They must have been a 3 wire plug. Anyway I connected the speedo wire coming from my pcm to the yellow & purple wires as chevy-art said and I still have no speedo. Not saying chevy-art is wrong,cause it worked for him. I must be doing something bass ackwards. Might have to pull the cluster like farmtruc said. Thanks. Still scratching my head!

[exboatracer]

I'm starting to think that maybe my speed sensor is bad. I also saved another plug that came from the old 700r4 trans that is a 2 wire plug, one wire is tan and one is purple with a white tracer. Does that plug ring a bell for anyone. Thanks again.Sorry to be a pita.

[gagliano7]

Do you have tuning software?If you have a speed reading in you tuning software then the sensor is good.Something may have to be changed in the pcm so you get a reading.You also have to make sure the yellow and purple wires are connected to your pcm so the computer gets a reading.
GREEN WIRE: PIN 20 in the RED Connector (VSS)



PURPLE WIRE: PIN 21 in the RED Connector (VSS)



YELLOW WIRE: PIN 50 in the RED Connector (speedometer)


On my truck a 1992 5 speed manual the wires from the trans sensor green/bk and purple/white went to pins 20 ans 21 on red connector to pcm.I have 1999 gmc pcm and wiring harness.Pin 50 red connector went to speedometer.

[exboatracer]

No, I dont have any kind of test equip of that sort. Here's what I found,in the red connector,I have a grn/blk wire in pin 20,a solid purple wire in pin 21, and a grn/wht wire in pin 50 that is labeled speedo. The speedo wire was left out of the harness intentionally for me to hook up.This wire-the grn/wht from pin 50 is the one I'm trying to hook up to the yellow and purple wires thats coming from c-100 in my truck's original wiring. Is this ok so far? Thanks for the help gag.

[Mickeymotormount]

I ended up using the dark green/white wire from pin 50 of the red connector and ran it right to the speedometer. I undid the guage cluster, pulled out the light blue/black wire that is in position S on the plug feeding the instrument cluster. I then cut the light blue/black wire that was in position S and soldered the dark green/white wire to the end of the wire so as to reuse the little connector and then reinstalled the wire back into position S on the plug. Voila, speedo worked.

Hopefully, your wiring harness is similar. I'm using a 1993 wiring diagram from a Chevrolet C/K service manual.

Do you have cruise control? If so, it's a slightly different setup.

Let us know how you make out.

[gagliano7]

Do you have pins 20 and 21 connected to the vss in your tranny?If not you will not get a reading on pin 50 .I connected pin 50 to the speedometer wire that came out of my drac box behind the glove box.I think the 1990 has a different setup.

Here is some good write ups that my help you out

http://www.ls1truck.com/forums/lsx-t...-wiring-4.html

http://www.ls1truck.com/forums/lsx-t...gmc-k1500.html

http://www.ls1truck.com/forums/lsx-t...eter-help.html

http://www.ls1truck.com/forums/lsx-t...eedometer.html

http://www.ls1truck.com/forums/lsx-t...eter-help.html

[exboatracer]

You guys are too kind,flooding me with all this good info. The first thing I'll do is check to see if pins 20 & 21 go to the vss plug and then move on from there. With all this help I know I'll get it working. Might take a day or two and I will let you know. Thanks again.