Self-diagnosing pressure regulator apparatus

摘要

A self-diagnosing shift pressure regulator apparatus for an automatic shift transmission provides a diagnostic output that reliably and timely detects initiation and cessation of fluid supply to a friction element (18). The regulator apparatus includes a pressure regulator valve (14) responsive to an electronically developed pilot pressure, and a diagnostic switch (16). The pilot pressure positions the pressure regulator valve in one of three states -- ON, TRIM, and OFF -- and the diagnostic switch is continuously activated by a control pressure whenever the pressure regulator valve is in the TRIM or ON states.