sounds dumb but check the seat switch and wiring for open circuit and frame contact, then check that the fuses are good and are all there. i have noticed an alarming trend of "stolen" fuses and it has given some tech's fits. they all check good but open holes are common so overlooked. the **** fuses fit cars and are very convenient. there are also some possible problems with the flow regulator valve in the contol valve but that's a pretty big job so kill the small s*&% first.