Refrigerator good, Freeze won't cool below 19 degrees F.

I have a 4 door GRQC2255AF refrigerator. I bought it as a scratch and dent, but there is no warranty on it. Found that out after contacting Frigidaire. The refrigerator cools to exactly where it is set, but the freezer never gets below 20 degrees F.

I have changed the freezer and the defrost sensors and the Power Control Board. That was a suggestion in a troubleshooting tree but I may have misread the Main board as the PCB. Diagnostics does not show any problem.

My question is where do i go next? Is the main PC board the most likely problem? Is there a way to test it besides the control panel diagnostics?