So I have been searching through the forums and doing my own diagnostics and no go. In my 1992 z28 everything is stock except the Prom that i tuned myself. The speedo was working with my newest tune and the cruise control has never worked since i have had it, and one day the speedo was bouncing all over the place and it just pinned at 0 and has been there ever since. Also the Odometer does not work. When i am driving and scanning the vehicle speed does indicate the correct speed so the VSS is working. These cars don't have buffers. No code 24. I tried to test if i was getting a signal from the ECM at the I/P lower driver side connector (C2) but i dont know what color wire it is!! The factory service manual has it backwards upside down etc... 1) does anyone have any ideas?? Can the: speedometer, needle, stepper motor (for the odo), etc. just go out??? 2) Does anyone know what color the wire is that sends the signal from the ECM to the guage is?? Thanks for any help. We have officially reached DEFCON 3.

it is gray

no the car is black.



just kidding the gauges are black yes...

The signal wire you were asking about...it is gray some years and others it is brown.

oh haha,
I get it now. I had a little bit of weed last night and i get illiterate when i'm high lol

Ill test her out today and see whats up. Should it be getting 12 DC volts when the key is in "RUN"? The reason i ask this is its supposed to flick up from the stop pin up to zero, so i assume its getting 12 normally then the signal (pulse) makes it go up and down??? Let me knoq if this is a correct assumption.

And thanks for the help!!

So i tested the Gray wire to ground (also gray) and key on engine on 0V, when i was driving around it got up to .06v. then i switched over to DCA and i was just driving through the neighborhood so i didn't go over 50mph but the amps got up to roughly .250dca, and i was kidding about the 50 mph, i was around 25-30...

So in conclusion the signal is getting to the gauge, but the gauge isn't doing anything. This calls for a replacement speedo gauge right??

http://www.thirdgen.org/techboard/at...tbispeedob.jpg Maybe this will help. I think you should test using ac

http://www.thirdgen.org/techboard/el...em-1991-z.html (Speedometer Problem 1991 Z Conv) Another good thread to read up on this stuff.....Let me know if you get it fixed cause mines broke too. lol

I have verified that the VSS is working, there is no buffer, signal is getting to the cluster... I think i just need a new cluster. i took it all apart to see if there was a loose wire or a crack in the printed circuit, and its all cherry, and the Speedo looks like its hardwired in... Does anyone have a 145mph cluster with a working speedo they want to get rid of??

BTW i know that the VSS is working because when i drive the car with it hooked up to tuner pro, it knows how fast i am going. In 92 there are two signals a 4000 and a 2000 pulse per mile. one is for the speedometer and the other is for something else, engine timing, iac control, fueling etc...

I just bought a used cluster from work and it'll take about a week to get here so i'll repost my results then. When i was ordering it there were 3 choices, 2 for the 5.0 and a different one for the 5.7??? does anyone know what the diff could be??

BTW while i had the cluster out i replaced some burnt out bulbs with those 194LED replacements in RED and holy sh*T!!! its like driving in an aircraft cockpit!! Nightvision!

So i wasn't able to get the 145 cluster from work... Anyone have any ideas on this prob?? could it be the speed sensor after all??? last time i logged the speed was coming up 100% accurate.....