This solenoid block is capable of failing at anytime and can be the cause of the codes and how it's operating. I have had to warranty solenoid blocks after rebuild with these transmissions due to a bad block setting codes, even after being gone for months.
I would check the connector to make sure there is no water inside it from the AC drip and check for bent or corroded pins, if all looks good my next step would be replacing the block. Once you have it out it might be worth it to check it with a meter, even if it electrically checks out it still could be bad...
I just got around to changing the solenoid block with a known good one that worked. I even rebuilt "Pressure Control Solenod A", "B" and 'C". Can't remember which video I watched on Youtube, but they did a good job showing how to make sure and fix the disc and pins so they weren't sticking. Shift Solenoids, "A", "B", "C", "D" all ohm out to around the middle of the Resistance Ohms range. 24 ohms (range 16-45), Pressure Control Solenoid "A", "B", "C" are also around the middle of the range. 5.0 ohms (range 3.3-7.5). TCC Solenoid Ohms out at 10.3ohms, (range 9-16) .
I tested the all the Solenoids with a 12 volt battery. Starting with power to the 3 male pin.
Shift Solenoid "A", Pins 3 and 16
Shift Solenoid "B", Pins 3 and 15
Shift Solenoid "C", Pins 3 and 6
Shift Solenoid "D", Pins 3 and 5
Pressure Control Solenoid "A", Pins 3 and 11
Pressure Control Solenoid "B", Pins 3 and 1
Pressure Control Solenoid "C", Pins 3 and 4
TCC Solenoid, Pins 3 and 14
All Solenoids had a strong clicking sound, which tells me that they are all working.
Before reinstalled the block, I checked continuity at the PCM connector, #13 female pin, in the middle of the 3 connectors on the fire wall to the #1 female pin at the transmission case connector. Continuity check out to be zero, so this tells me there is no open circuit.
So far I have replaced the Valve Body, rebuilt and replaced the Solenoid block, and replaced the OD Servo. When I rebuilt the transmission, I had the new brass bushings installed in the case servo bores. I'm still have a high shift into 2nd gear and the TCC is not locking up, with the P0775 code.
So frustrating. In my ATSG transmission book, a P0775 is defined as a Pressure Control "B" solenoid, shorted circuit. Do I need to start looking for shorts in the harness? What is the best way? Or could my PCM not going to ground on Pin #13 at the middle PCM connector?