I checked for tsb's regarding the code and issue. I would say since you had the pressure control solenoid changed there has to be a connection or wire harness problem. Here is electrical schematics.
The picture won't come up for me. I just has a little box with an x in it.
I fround another tsb.
APPLICABILITY:99 MY & 2000 MY Legacy, Forester, and Impreza Vehicles.
SUBJECT:TCM Trouble Code 38 (Revised)
In the event you encounter a customer complaint of the A/T temperature light flashing and this code is found in the TCM, perform the following:
First, eliminate all wiring and connector concerns by performing the tests as outlined in the appropriate Service Manual for this code. Repair as necessary.
After you have checked and confirmed these items, and you still did not find any problems, we recommend you replace the part(s) as shown.
Here are better pictures