Patent ID: 7651427

Claim:
An electro-hydraulic control system that controls engagement of torque-transmitting mechanisms in a transmission; wherein the control system includes a controller, comprising: a pressure switch diagnostic system having first, second, third and fourth pressure switches each having a high and a low logic state; first and second logic valves each movable between a respective first position and second position; first, second, third and fourth trim valves each movable between a respective first position and second position; wherein two of the pressure switches are each multiplexed to report one of the high logic state and the low logic state to the controller in accordance with a relatively high and a relatively low fluid pressure, respectively, at a respective one of two of the trim valves corresponding with the position of the respective one of two of the trim valves and the position of the first logic valve; thereby enabling a determination of a change in position or a failure to change position of the respective one of two of the trim valves or the first logic valve; and wherein the other two of the pressure switches are each multiplexed to report one of the high and the low logic state to the controller in accordance with a relatively high and a relatively low fluid pressure, respectively, at a respective one of the other two trim valves corresponding with the position of the respective one of the other two trim valves and the position of the second logic valve; thereby enabling a determination of a change in position or a failure to change position of the respective one of the other two trim valves or of the second logic valve.