pdqford -
Where is the resistance that brings down the voltage to the 2.6-5 volt range - PCM or TRS?
The TRS was changed so I'm thinking it's not there.
What voltage change is the PCM looking for on pin 64?
Does a voltage change on pin 64 tell the PCM to read a new gear position?
Does the PCM determine what gear position is selected by reading signals on various combinations of pins in the TRS connector?

 

How Do You Fix A Fault Code P0708? - Blurtit


I don't know just how the PCM interprets the gear position.
The DTR has 4 switches and a 270 Ohm resistor for determining the six possible gear positions.
It also has 3 independent switches: one turns on the reversing lights when in reverse, one functions as a neutral start switch when in Park or Neutral, and one is used if A4WD to allow entering Low Range when Neutral is selected.

 

The article you listed is great. I was having trouble with the point you mention in the quote about the voltage going over 5 volts. After rereading the 2 articles I think it's clearer. The reference of 5 volts comes from the PCM. There is really no way it could go over 5 volts unless is shorted to a 12v wire somewhere or the PCM is bad, not likely. The 1st article says "the range sensor is indicating a high voltage drop or high resistance", not a voltage higher that 5 volts. I think you can run a voltage test in the driveway - wheels blocked, parking brake set, brake pedal set - looking for "Expected values are: P) 4.4 volts R) 3.6 volts N) 2.9 volts D) 2.0 volts 2) 1.4 volts 1) 0.7 volts". This would show the switch is basically working fine. Since the problem only occurs when driving (vibration) a road test would be next to monitor for stable voltages.
My guess is since the TRS was replaced and the problem persists a very thorough wiring harness inspection is next. Particularly since the the engine has been replaced. Also, check for good ground connections. I found 6 or 7 wiring harness/hose rubbing issues on my 2002 Excursion and 2003 Expedition. Both looked like that had not been disturbed from factory. Non were actually causing any problem, but would have if left alone.

 

I will go with that, next time I get to the shop I will trace the wires better. I looked them over, pulled each connector and inspected the connections. I will try to trace the wires all the way from the position sensor to the pcm and see if I can find a place where it has rubbed or been compromised.
If my memory is correct, when we put the new engine in we did pinch a wire. The tranny would not line up until we backed the tranny back and moved the wire. Possibly pinched a wire then and it took 3 years to show up? It did start the jumping and shuddering a few months after the engine change, but that has not gotten worse until last weekend. Maybe we pinched a wire and it just now rubbed and is shorting?
Also, it does the shuddering worse when under a load. I drove it today on a fairly flat road. Set the cruise at 65 and went, no issues at all with the running except for the warning lights on. I went about 100 miles without an issue, when my wife drove it 20 miles after that she reported it was bucking and running bad all the way.

 

Well, I gave up. I traced the wires and inspected every inch closely and found no smashed places, torn insulation, pinch points or rubbing. I couldn't find anything wrong there at all, so I threw in the towel. Went out and got a 2005 F350. It will tow our camper better, and is in a lot better shape!
I kept the expedition for now and will mess with it more in the spring, but for now it is retired to the run around vehicle. We will use it around town and for my daughter to drive, but I don't feel comfortable enough to run it out of town.

 

I am pretty sure that if you invest in a bluetooth scantool, either OBDLink MX or another equivalent, you can use the program FORScan to check what the PCM is reading from the DTR switch, this could even be monitored while driving.

 

Where could a guy find a Bluetooth scan tool? Would that work on a 2001 vehicle?
I have not given up completely yet, but will wait for warmer weather to mess with it again. If I can get it reliable again it will go to my daughter when she turns 16 this spring.

 

Here's one of the best you can buy:

 

Thanks for the link, that isn't too bad of a price.

 

Or purchase one of these then download a $10 app through iOS or Android and save $80.

 

There's a reason one is more expensive than the other.. Specifically, support for MS CAN protocol (might not be relevant on a 1st gen), and performance. The cheaper dongles tend to be quite slow compared to the more expensive ones, due to superior chips being used in the latter ones.

 

I like the price of that one, if it will do everything I would want. I would want something I can connect to my 99 F150, my 01 Expedition and if possible also be able to use on my 05 F350.
If not, for the price if it only worked on my expedition it would be worth it. It is 60 miles to the nearest parts store that will do a free scan.
I think I am probably done working on the expedition for a while. Winter weather is coming in fast and my shop is not big enough for the expedition to fit under the door, so I am stuck working on it outside.

 

The OBDLink can access the MS CAN, which is necessary if you want full access to the '05 F150. It supports all kinds of vehicles, there's many different softwares for different makes, and Torque or similar which supports everything. FORScan in a Ford/Lincoln/Mercury only software, with some support for Mazda and other Ford-owned makes since they share a lot with Ford.

 

Here is an update to this old thread.
I got the expedition in the shop and up in the air to get under it. I discovered a couple of things. First off, my ohm meter is not working! So, I decided all of the resistance tests I tried to do back in November were worthless.
Next, I got to a position where I could see the wiring harness better. I was inspecting the wrong wires! The wires I needed to be checking ran over the top of the transmission and up the passenger side. I was checking the wrong wires the entire time.
Finally, and the solution to my problem! The wiring harness had come in contact with the exhaust manifold on the passenger side. It melted through the wires. 4 of the wires were bare and 2 were broken. They were shorting to ground and shorting to each other. I got that fixed and my problems may be solved! No codes or flashing lights anymore!
I am suspecting this may have been a cause of my other issues with the bucking while driving. If the right wire shorts out for an instant against the manifold I suspect it could cause the transmission to do bad things, giving me the feeling of the vehicle bucking for just a brief instant.
I haven't taken it out on the road yet, still searching for a battery drain, but I am going to have to replace my meter before I go further with that problem.
Thanks to all of the help on here, without this advice I would not have re-checked the wires and would still be scratching my head over this.

 

Battery drain found (in the radio), transmission issue solved, and I found the misfire I have been chasing for the past few months. Finally found which coil was going bad. Problems solved, back on the road.