Pressure Regulating Solenoid: Description and Operation

OPERATION
Fluid flow within the transmission assembly is controlled by three solenoid valves and five pressure regulators.
Regulators and solenoids are supplied +12V via FET (high side switch). Control of the solenoids is effected by switching one side to ground through the Transmission Control Module (TCM). The pressure regulators are controlled by a Pulse Width Modulated (PWM) signal from the TCM.

MONITORING PROCEDURE
During the initialization, the TCM cycles the FET 'on/off ' and measures the O/P voltage. Following this test the TCM switches the FET off until an engine start is detected. Should a fault be detected during this cycle DTC P0702 will be logged.
During normal operation, the TCM monitors solenoid, regulator and FET 'switch on' but does not check FET 'switch off '.
Voltage is monitored at the regulators and solenoids for continuity and shorts. For example, when a solenoid is ON the voltage on the TCM side should be ground, when OFF, the voltage should be +12V.