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 DC pressure switch when off (when the corresponding friction element is not applied) by briefly applying the DC element which will cause the corresponding pressure switch to close. The test verifies that the switch is 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.