Theory Of Operation

Pressure switches are normally open (off or no pressure applied) and read high (+12 volts). When an element is applied, the corresponding pressure switch closes to ground (0.0 volts) or turns on. The controller tests the LC pressure switch when it is open (when the corresponding friction element is not applied) by briefly applying the LC element which will cause the corresponding pressure switch to close. The test verifies that the switches are operational and that the switch will close when the corresponding element is applied. If a switch fails to respond to two consecutive tests, the transmission system defaults to limp-in mode and illuminates the MIL.