12valvewagon91

Ok,,,, My 91.5 12 valver is a little testy. I can drive it and hit a hard bunp and the speedo will decide to work, then if it sits overnight it will not work at first, then unexpectedly it will work. I thought a bad VSS, so I put a new one on the truck, NOTHING, I pulled the sensor off, and ran on jack stands, and the square drive is turning. I traced wires and tested as far up the bell housing as I could reach. Have continuity on both for a ways up, and cant test much farther.

The Black wire with blue tracer seems to be shorted to ground, or it is the ground because I have continuity from the plug end to the tranny case. So im assuming itsnormal. The other wire, white with an orange tracer is ok as far as I can go up the tranny.

What else runs with the VSS, Is there a chance I have a bad OD solonoid?

Am I missing something here???

Kasey

Onemoparnut

Do you have cruise control and if you do will it work when the speedo is not working?

12valvewagon91

No cruise when speedo is dead.

Onemoparnut

Ok so that means it is not the speedo itself. The problem is in the vss or the wiring somewhere so I can't be more help.

12valvewagon91

IS it possible I have a wireing issure up in the dash?

What could it be if the Cruise worked when speedo was dead? Just a bad cluster?

Onemoparnut

I don't think the problem is in the dash at all cause the cruise don't work when the speedo quits. If the cruise did still work then that would mean that the pcm was getting the signal from the vss and the speedo was not getting the signal or not working. Since you lose cruise with the speedo that means that the pcm is not getting the signal from the vss. Your problem is either with the vss or the wiring between the vss and the pcm. Did you replace the plug for the vss when you changed the vss? They are known to be trouble. Maybe try cleaning the connector at the vss and using some dielectric grease on the connection.

12valvewagon91

My plug looked good, no discolor, or corrosion, But I have some contact cleaner, Ill do that.

Kasey

12valvewagon91

Could it be the SBEC controller? Is there a was to do a simple test to rule that out?

Onemoparnut

What is a sbec controller?

12valvewagon91

I measured continuity from the SBEC controller under the fender drivers side to the connector at the speed sensor, and both are good. Now if I measure the black wire blue tracer with it unplugged to chassis ground i get nothing, but when its plugged inn i have continuity at chassis ground.

Im wondering if the conputer "SBEC" is bad and shorted to ground???

Kasey

12valvewagon91

I think I found my issue, the "new" VSS from Napa is not producing .5 volts ever when I spin it over.

Hope thats all the issue is, I had them order a new one.

Kasey

Barney428

Post back how this works out. Mine quit two years ago. I have replaced the gears in the speedo and the vss and still nothing

sootnsmoke

very interested in the result as well

12valvewagon91

ok, today I got the new VSS from napa, and it makes voltage. Installed it, and nothing. Soo after testing my speedo, and verifying its fine, Im gonna go ahead and buy a new, reman SBEC computer. I can think of nothing else that would cause this issue.

Kasey

ppiggppenn

Question still on the floor "What's a SBEC controller?" ... my problem turned out to be water getting into the VSS block terminal, solved with contact cleaner, filling the contacts with dialectric grease and sealing the outside where the wires enter with silicone goop. When you spin the speedo shaft with a drill does the speedo react? Mine needs the "ignition" to be on for this.