2004 Grand Cherokee no TCC engagement

[Jimmy]

Changed thermostat because wasn't running up to temp. Now fine but still no TCC Lock-up. TPS, Man vac, trans temp, and other data look normal. But governor pressure not keeping up with Desired when driving conditions would normally engage TCC. des gov press closely matches gov press during take off and all upshifts, psi from zero up to around 40psi. But then duty cycle drops to 1, des gov pressure goes to 127 (which I believe is normal), but actual gov pressure only makes it up to 68 or so psi. Pressure/pump failing? Is there an external method of actually measure this pressure? Pressure sensor seems dead on for all the lower pressures... drives and shifts perfect other than never engages tcc. No codes present. Thanks if anyone has information!