speedo not working

I have a truck that came into my shop with the speedo not working. I get mph on my scanner so i swapped in another gauge cluster that is supposedly good, still nothing. does anyone have a wiring diagram for the dash? Also could the pcm be the problem, maybe not sending a signal out to the dash? anyone have any ideas?

Vss sensor rear axle


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Jaredkeller96 said:

Vss sensor rear axle


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Nope, if he's able to get the speed reading on his scanner then the VSS is working correctly.

ToMang07 said:

Clock Spring?

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Isnt the clock spring for steering wheel controls and airbag?

Jaredkeller96 said:

Vss sensor rear axle


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MPH is registering on my scanner so im pretty sure that rules out the VSS.

I wanna say yes to the clock spring being for airbag


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just happened to pull the GEM codes, good god this thing is a mess.
GEM
c1125 brake fluid sensor input circuit fault
b1352 ignition key in ciruit fault
b1300 pwr door lock circuit fault
b1310 pwr door unlock circuit fault
b1318 low battery voltage @ module
p0500 vss fault
b1483 brake pedal input circuit fault
b1371 illuminated entry relay coil fault
b1302 accesory delay relay coil circuit
b1982 driver side door unlock relay circuit
c1182 park lamp flash relay circuit
b1323 door ajar lamp circuit
b1450 wiper washer delay switch circuit fault

ABS system
c1226 brake warning short to ground
c1230 rear speed sensor circuit fault

air bag
b1318 low battery voltage at module
b1392 drivers air bag high/ res circuit open
b1869 airbag warning indicator lamp circuit open

Also noticed the truck has no brake lights, will check power to switch on brake pedal and see whats up with that. All codes return almost immediately after clearing, this poor kid got ***ed up the corn hole on this thing. Still not sure why we have a rear VSS fault, its working or at least displaying mph on my scanner. Its one of the most jacked up trucks electrical wise that ive ever had through the shop.

can you find evidence of damaged/molested wiring? Almost sounds like an accessory was poorly installed, theft damage, etc

Found a couple wires cut on the harness where it comes over drivers side frame rail and connects to the main harness on the d side inner fender. One broke is the signal wire from the vss..... Not sure what the other 2 are, can't find them in the poor diagrams I have


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With that many codes, who knows how long they were in there. All of the past GEM conversations Ive seen had more to do with bad voltage, shorted batteries, leaking windshields, etc. A systemic issue and resolution was not easy... yes, poor kid or maybe you... lol

Particulars of the truck please. 2wd, 4wd, ABS and model year.

All make a difference how the speedometer is controlled.

907DAVE said:

Particulars of the truck please. 2wd, 4wd, ABS and model year.

All make a difference how the speedometer is controlled.

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Early 99 ext cab 4x4. Up until now all codes would return almost immediately after being cleared. Now only a few minor codes return. No abs, brake or cel lights on dash now


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Did you get anywhere with this? My speedo quit working but my odometer still works. Any of these trucks get vss from front axle? I did a 05 axle swap but have not got the abs plugged in yet.

They all have a vss on the rear axle right on top. I'm guessing if your odometer works but your speedo doesn't then the stepper motor for your speedo is dead.

dbunyip said:

Did you get anywhere with this? My speedo quit working but my odometer still works. Any of these trucks get vss from front axle? I did a 05 axle swap but have not got the abs plugged in yet.

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Yeah I got the odometer and speedo working. Was broke vss signal wire


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Short Bus said:

Yeah I got the odometer and speedo working. Was broke vss signal wire


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I also am having issues with the speedo and odometer, I have swapped out the vss sensor made sure there was a good connection, traced the wire as far as I could. Everything was good.
I also took the cluster off to see if there was a bad connection but looked good.
Idk where to look next.
Is there a fuse or anything that could be helpful for my situation.
It's a 99 f350 7.3l

Any ideas will help!
Thanks!

Behind the driver side headlight there is a ground bolted to the core support that may have come loose. Caused my 03 to do all kinds of funky stuff with the speedo. Don't know if its the same on a 99 but its worth a shot?

farmall99 said:

Behind the driver side headlight there is a ground bolted to the core support that may have come loose. Caused my 03 to do all kinds of funky stuff with the speedo. Don't know if its the same on a 99 but its worth a shot?

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Thanks I'll look into that tomorrow and let you know if I find a problem there!