Yeah it is possible...
That is the line pressure tap location from the manual.
In your manual, go to Group 3 (powertrain) / Section 307-1 / DIAGNOSIS AND TESTING / Special Testing Procedures / Line Pressure Test.
There you will find the image above and a pressure table. There is also a Air Pressure Test and Testing Procedures.
I agree with your "open heart surgery" thing. Like I said, I don't think he has a hydralic problem. But it would be a good idea to do, just to get a better picture of what is going on. You would have to troubleshoot the code first and then worry about any line pressures later.
