Working on a 2000 F550 with a 4r100 with a pto. The problems I'm having make no sense to me. I have a code p0715, and p0717 which leads me to the turbine speed sensor/circuit. When I hook the scan tool to the truck and watch the sensor it shows zero speed until the truck shifts into overdrive, and then it reads normally. Once it shifts back down to third it never shows any speed for the rest of that ignition cycle. Turn off the ignition and drive it again and you have the same results- No turbine speed until overdrive, then it goes away once it shifts back down to third.
I have installed a new sensor and pigtail, tried another pcm, and ran ohm checks on both wires coming off of the sensor. I keep thinking its a wiring problems that i'm just not finding, but it has a definate pattern that makes me believe it something else. Also, my output speed and range sensor are both functioning normally. Any ideas guys?
Thanks

 

Yea I think you have a strange issue with this one. Have you back probed from the computer to the speed sensor to check for a problem in the harness?

I should be able to come up with a pin out chart for you if you dont have one.

I have checked all my data bases for this kind of issue and came up empty, I would look very closely at the harness from the trans to the computer, there has to be a short somewhere there.

 

I have a ford repair manual/wiring diagram, and that is what im using for reference. I probed both wires from the sensor(1, back to the pcm; and the other from the main trans harness) and had no open circuits. Since then I bought another pigtail for the sensor, and ran new wire straight to the pcm and trans harness. Same problem. I put it up on stands here in the shop, ran it up to about 50mph, and you see turbine speed when it shifts into overdrive. Turn the overdrive off and it goes away, turn it back on and turbine speed comes back. When I slow down and the trans shifts back to 3rd gear you loose it also. It seems way to regular to be a loose/bad connection to me, but i didnt see anything in the wiring diagram to make me believe it should matter what gear the trans was in.

 

How about unplugging the trans connector just to see if you get speed signal.

The trans should be in third with case connector unplugged.

 

Unplugged the trans connector and I still have no speed signal.

 

The GY/RD wire is a dedicated sensor ground circuit. The DG/WT wire is the sensor signal.

Try to ground the ground wire somewhere else, just to rule out a circuit ground issue. Like straight to the trans case.

Your wire color may be different, I found that info from a 2000 f350 7.3l