You will need to install a line pressure gauge to continue troubleshooting.
Check to see if line pressure is between 50 and 80 psi at idle (depending on your controller's calibration and the valve body calibration).
Also check to see if line pressure increases as soon as the throttle begins to open.
With the ignition off, disconnect the solenoid harness from the controller. Then, start the engine and maintain a fast idle speed of about 1500 RPM. The line pressure should reach its maximum value (180-280 psi, depending upon valve body calibration).
If line pressure is always high, check the resistance of the pressure control solenoid (PCS or EPC solenoid).
Before testing, touch the test leads together. The meter should read zero or close to zero. If it reads a number, for example 5 ohms, then you will need to subtract 5 ohms from each reading.
With the solenoid harness unplugged, measure the resistance between pins 6 (red) and 1 (light blue). It should measure between 3 and 7 Ohms.
