Pin #38 on the 14 pin connector of the TCM is the solenoid voltage supply which becomes pin #6 on the transmission harness.

This is the limp mode strategy, once the TCM detects a transmission operating fault or a network input fault from the engine and chassis management systems, the transmission control module turns off (pin #38) all power to the solenoids in the valve body. That’s why you have NO VOLTAGE at pin #38. Working pressure is set at maximum value; the transmission is locked into the gear it was in before the fault occurred.

If you stop the car, turn if off, wait at least 10 second then restart the car move the lever into Drive, the transmission will fail safe into 2nd and reverse gear. The transmission will stay in Limp mode until the malfunction is fixed and erased from memory. Some codes reset automatically or by key reset.

Unique shift pattern:

The 722.6 transmission shift solenoids are an on /off solenoid and stay OFF to control the gear they are in. If You’re driving and the transmission control module commands a 3rd to 4th gear up shift, the y3/6y4 solenoid is switched from OFF to ON and OFF again to make the shift. While in 4th gear the y3/6y4 solenoid is OFF, no voltage.

This explains why, when the transmission control module detects a fault while the car is being driven, the transmission is locked into the last gear it was in before the fault occurred until the car is turned off.

I would remove the pan and check for any signs of a transmission failure and while you are in there get all the numbers from the valve body. To diagnose