Alright, still nothing. The truck is on jackstands, the new sensor is in, the wheels are turning, the ABS light has gone out but STILL no speedo. I backprobed the sensor feeds and am getting 0.67 volts. Nothing to C2, Pin 27 either. Thoughts?

 

Also, I checked the power supply to the ABS module. 13.5 volts with the truck running. Just thought I'd throw that in too

 

With the sensor unplugged, I get just shy of 5 volts..

 

The five volts should be the supply side TO the sensor, if you are getting five volts back on the signal return line, you have a short somewhere. What does voltage do as you vary the speed?

And wonder if it isn't time to check and see if you are getting speedo signal to the cluster...... but, I would think that would give you a no bus error...... If you have a scanner you can plug in, take it for a drive, and see if it registers anything for vehicle speed.

The wiring diagrams for this type of diagnosis SUCK.... really need the second manual.... Would be nice if someone could upload those as well.

 

Okay, here goes...
ABS module plugged in, rear sensor plugged in, truck on, wheels spinning: 13.5 volts on both legs coming in(power to abs module), backprobed red/violet speed sensor output. Got 0.67 volts. Nothing on return. Unplugged sensor, red/violet jumped to 4.8 lolts, key on, engine off. White/orange wire dead the whole time

I also plugged my scanner into the diagnostic port. Says no mph.

 

I suspect you have an open in the wiring back to the sensor, where the wire itself is broken, but, NOT the insulation around it.... Try plugging it in, and dinkin' with the harness and see if the speedo jumps.

Obviously, be EXTREMELY careful of things down there that are moving........ NOT something to be done by yourself.

 

Alright, I think it's fixed... kinda. I replaced the ABS module and most of the speedo wiring. It works, but I gotta drop the fuel tak to route the wires properly. Now, here's the odd thing: I had to re-reprogram my truck to get the speedo right. And it took a lot longer than normal for my PCM to "learn" the truck. And my shift light keeps telling me to upshift, although I'm in high gear. Do I need to get the replacement module programmed as well?