'94 Speedometer Stopped Working

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Brentbba

Brentbba

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Was up in Big Bear this weekend for Mountain Rendezvous this past weekend. Started the truck Saturday morning to go out for a run and the speedometer/odometer was dead. All other gauges, RPM's were all working. Only reference on a quick look in the FSM was to a speedometer cable, but search here in the 80's section references a speed sensor on later models also.

Suggestions? Is it just a speedometer cable or a sensor? Easy fix?

I've got two weeks before next outing and would really like to have a working speedometer.
 
'94 has sensor...

If it is the sensor, its a simple fix, but test the sensor first...!

The sensor is easliy reached from underside, 5 minute replace job... But is not what I would consider a cheap sensor either.

My '94 speedo is out too after some river xsings! but the sensor is NOT the problem! :(

It's been like this for a while now, with no ill effects that I can feel anyways...
 
Try cleaning the sensor connection with electrical connection cleaner and then use dielectric grease in the connection before you reconnect it. See if that helps your issue.
 
Did finally find diagnosis info in the BE (Body Electrical) section of the FSM. Points to speed sensor #1 as the primary culprit of the speedometer not working. Will try to find the thing to pull and test. Simple diagnostic test in the FSM to perform.
 
If your sensor is broken it has other effects. The transmission needs that sensor to determine shifting points. When I broke mine on the traill, a light on my dash was blinking. I think it was the N light.

I've also had my odometer/speedometer go out. When I took it apart the little plastic teeth were very worn. I have a '93 and everybody said '93-97 cluster would work. They were wrong. Lights were completely different. I ended up taking the speedo/odometer out of the 94 and and installing it in my '93.
 
UWdave said:
If your sensor is broken it has other effects. The transmission needs that sensor to determine shifting points. When I broke mine on the traill, a light on my dash was blinking. I think it was the N light.

I've also had my odometer/speedometer go out. When I took it apart the little plastic teeth were very worn. I have a '93 and everybody said '93-97 cluster would work. They were wrong. Lights were completely different. I ended up taking the speedo/odometer out of the 94 and and installing it in my '93.
Click to expand...

Thx - Drove it on and off road all day Saturday and 90 miles home on Sunday with no ill effects that I could detect or feel. No blinking O/D or N lights on the dash either. If the teeth at the cluster were worn, wouldn't I have heard some sort of grinding or just worn to the nubs over 18 years and 223K miles.

Guage was just dead when I started the truck Saturday morning. Didn't notice it not working driving up to the mountains Friday either.

Still need to crawl under the truck to find the #1 sensor and see if perhaps a random rock damaged the harness in some way too. Doubtful as I was only on a dirt/rocky road for about 1/4 mile into the campsite Friday.

Easiest test will be the sensor. Guage cluster will be a PITA to remove, so I hope it's not that! Only good side of that would be that I could replace the burned out D light!
 
But if you transmission is working normally, it can't be your sensor.

I looked back at my records and my cluster problem was the odometer only. Sorry about the confusion. I was getting horrendous fuel economy, then I realized the odometer would randomly sticking at 114 or similar, then it stopped working all together.
 
UWdave said:
But if you transmission is working normally, it can't be your sensor.

I looked back at my records and my cluster problem was the odometer only. Sorry about the confusion. I was getting horrendous fuel economy, then I realized the odometer would randomly sticking at 114 or similar, then it stopped working all together.
Click to expand...

I suppose it still could be the sensor? Speedometer/Odometer/Trip Odometer all kaput at the same time.
 
My '94 has been with no speedo for a long time and tranny shift just fine, I cant tell any Ill efects but there might be some minor shift point errors, I for the life of me cant feel any and I wheel it like this!

Does this '94 have more thatn 1 speed sensor? one for the speedo and another for tranny/ecu?

And yes '95-'97 cluster is diferent thatn the '93-'94 cluster, but if you open up the 95+ cluster, you can remove the speedo from it and install it on the '94 cluster... the internals are the same...
 
Brentbba said:
I suppose it still could be the sensor? Speedometer/Odometer/Trip Odometer all kaput at the same time.
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One sensor feeds both the cluster and the transmission. After the sensor, it splits somewhere and one wire goes to the cluster for the speedo/odo/trip and another wire goes to the transmission ECU. This is why you need to install speedometer correction near the sensor, so both the cluster and the trans ecu get the "corrected" signal.

If speedo and transmission aren't working right ---> sensor

If speedo is not working and transmission is ok ----> cluster or wiring after the split

If speedo is working and transmssion is bad ----> trans ecu or wiring after the split
 
Pulled the speedo correction gear out last night - teeth on it look as good as the day I installed it. Still have the OEM and instructions from Slee in the garage!

Hit the sensor itself with some PB Blaster last night, so will get it unscrewed tonight hopefully and give it a test.
 
Found the cause - key shaft from the sensor is sheared off. Shaft it slides into on the t-case side spins just fine, so the sensor has to have siezed. New sensor on the way in the morning. :crybaby:
Speed Sensor #1.webp
 
Beat me to it. That was going to be my guess. Be sure you are getting a new O ring with it. You'll be dismayed to find when properly installed with a new O ring the sensor still seems "loose" in the mounting. I've done 2 and it seems to be normal. Spendy little buggers.

DougM
 
IdahoDoug said:
Beat me to it. That was going to be my guess. Be sure you are getting a new O ring with it. You'll be dismayed to find when properly installed with a new O ring the sensor still seems "loose" in the mounting. I've done 2 and it seems to be normal. Spendy little buggers.

DougM
Click to expand...

Doug - long time. I see no o-ring on the sensor itself. There's a big o-ring on the piece that slided into the transfer case.
 
So it looks like I was very wrong. But I'm confused how.

How did this not drive your transmission into limp mode?
 
UWdave said:
So it looks like I was very wrong. But I'm confused how.

How did this not drive your transmission into limp mode?
Click to expand...

Speedo gear in the transfer case is still spinning, just the portion to the speed sensor itself that sends the electronic signal to the instrument cluster speedometer that stopped working/sheared off. Per the Shaman, that little black piece 'should be' pressed into the sleeve that holds the speedo gear into the transfer case, so replacing it also. That part is way inexpensive compared to the sensor - about 10% of the cost!

I know - others have noted different shift points, etc. I drove about 30 miles + each way to the trail head, couple of hours on trail and another 90 miles home the next day and did not notice any difference in the way the truck sounded, shifted or drove. To/from and on trail windy mountain roads and freeway most of the way home so lots of varied driving conditions and no difference to me...and I have lots of seat time in this truck - 18 years and 223,000 miles worth.
 
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