ChatGPT says:

I've been using ChatGPT for a while on this, and its been helpful, but to a point.

 

This is a good idea, though I'm thinking that there is more of a rat problem than a water problem. If a particular module was not getting power thats much easier to diagnose than when it has power and isn't working right. ie. no ECM, PCM, fuel pump, no start

There is another detail that I haven't mentioned to avoid overcomplicating the story, but I was waiting a month for an appointment to fix the engine mounts, so when I brought the vehicle in I added that it wasn't starting. They got it started and then replaced the engine mounts, and then they came to me with the transmission codes. I assume they pushed the car onto the lift, got it started, and then replaced the engine mounts. No one suspected such an issue. Then they drove it off and noticed the issue with the transmission. So, however unlikely, it is possible that the transmission issue happened while replacing the engine mounts. Doesn't change much either way, can't prove it, doesn't change anything.

The main suspect, the mechanics told me that it is not the case, should be the wires between the PCM and the transmission. They said "no, it must be something mechanical inside the transmission, the wires are fine." Either that, or just replace the PCM, but the PCM is dry, never seen a drop of water.



The PCM (I think)

 

4 Connectors, I will include all 4 below:
1) Transmission Harness



2) Range Sensor:



3) TSS:


4) OSS:



Location shown below:


Pinpoint Test index page shown below:


I gave you Pinpoint E previously, the P1747.pdf I renamed to. Download Pinpoint-ALL.pdf to see all A to H.
Routine index page shown below, download Routine-ALL.pdf to see the routine number.




Now let's get to PCM:


C175 above and C2176 below:


Download PCM-Connector-Views.pdf to view the PCM pinout. You need that when testing 4 transmission connectors above (transmission harness, range sensor, TSS and OSS).
To check the DTC download DTC-ALL.pdf and DTC-Pinpoint-ALL.pdf.

 

It might be a good idea to check the trans fluid level and if it smells burned which is important.

You might be able to move the truck stuck in first gear, but certainly not good to drive it any distance constantly lugging because the parking brake was applied.There is a good chance it became overheated and that is the worst enemy of an auto trans. The trans shop was wise not to touch that trans because if they overhauled it , it still has some serious problems and driving it that way only makes more things go bad and increases the cost to correct.

Electrical sections need to have the correct amount of electrical power available to function as designed and if not available, for whatever reason, problems develop and cost to repair goes up the more it is driven.
The codes are telling you what is not working as designed and SOMEBODY needs to check and verify that correct electrical power is available for all those components which are affected ( The codes) . Do you think you have the equip and background to do this verifying ?

 

Shop told me that the transmission fluid is like-new. I'm guessing the previous owner replaced it at 50k miles (now 53).

Right now, I'm thinking that it is 2nd gear, even though I've selected 1st, due to the speeds. Not sure what is in D and 2, but they don't work too well.

I'm not yet following how the parking brake is connected to the transmission or the burnt wires, or if it was a coincidence. Only drove it 10 feet.

I desoldered and replaced a horizontal stabilizer chip on a projection TV in high school, then re-assembled all the components and wires from memory, and spent a portion of my life watching Macbook repair on Youtube. That being said, I've not yet successfully unclipped any of the connectors in the engine, such as the one pictured above. Looks like it needs a screwdriver and one turn too much and it will snap.

 

Thanks for these images, they are helpful. What program is this?

Does this 12 pin connector go directly from the transmission to the PCM, or is there another harness for the PCM where it intakes the transmission wires?

 

[AllData, mine covers any car make up to 2007 and incomplete info up to 2009

Yes, check post # 13, my long post. From the top you can see 3 diagrams labeled 30-1, 30-2 and 30-3, check 30-2 and 30-3 you can see C175 is the PCM connector, C167 the range sensor and C168 the 12-pin connector you talked about on 30-3.
The 4 connectors, all 4 of them I included the 12-pin connector to the matching PCM pin on the right.

There might be mechanical problem, but I wouldn't drop the pan until all the electrical stuffs are sorted out. It would be helpful if you have a scanner and a bluetooth adapter to read all the Ford's specific DTC and the live data. OBDLink MX+ for instance, you can read 100+ PIDs on just transmission only. For example:

 

FORScan full version on a laptop is the best choice IMO.

 

I took a look at the connectors today, and all the wires inside the engine are looking good, a little dust, but not chewed and mostly in their rubber/plastic housings.

I found that fuse 23 was blown, and that is labelled engine control.
From the Manual >>
22 20A* Engine control
23 20A* Engine control (gasoline engine only)/Climate control (Diesel engine only)
302 Full ISO relay Powertrain Control Module (PCM

I'm not sure what is the difference between "engine control" and "PCM", and why there are 2 fuses for it. I'd have to assume 23 was out before/during the drive, so either it is not engine control, or it is not essential to drive with at a bare minimum. Anyone know what it is?