Component Functional Description-Rear Drive Module (RDM)

Courtesy of CHRYSLER GROUP, LLC

The Drivetrain Control Module (DTCM) drives the actuator motor to apply the clutch and spin up the propeller shaft before the PTU is engaged during a transition from FWD to AWD, and when torque to the rear wheels is required. An H-Bridge inside the DTCM is used to rotate the bidirectional actuator motor on the RDM assembly to apply and release pressure to the torque transfer clutch inside the RDM. The DTCM can control the amount of pressure applied to the clutch inside the RDM, varying the torque applied to the rear wheels as needed. If the DTCM detects an overheat condition in the motor winding or calculates that the clutch temperature is too high, the RDM will be commanded off, disengaging the clutch until the temperature returns to a normal threshold.

• The actuator motor has two internal position sensors that count the rotations of the RDM actuator motor.
• The actuator motor has an internal temperature sensor to monitor the motor winding temperature. The module calculates the temperature of the torque transfer clutch based on the pressure being applied to the clutch and the intervals of the applications.

The common position sensor supply voltage circuit feeds the two internal position sensors in the actuator. The position sensors also share a common sensor return circuit. The hall effect position sensor signals are monitored by the DTCM during operation of the actuator to determine the amount of travel of the actuator motor. The internal temperature sensor operates like a typical two wire temperature sensor with a 5.0v signal and sensor ground circuit.

The DTCM monitors feedback from the temperature sensor and two position sensors inside the actuator motor. The sensor signals are monitored for circuit faults. If no circuit faults are present, the DTCM monitors the position sensors to determine that the torque transfer clutch position matches the position that is being commanded.

The RDM clutch classification and clutch energy specification are stamped on the RDM. These values must be programmed to the DTCM when a DTCM or RDM assembly have been replaced.  Failure to do so will result in a DTC. The RDM motor and clutch assembly are a matched set used to create the clutch classification and clutch energy specifications. For this reason, the RDM motor should not be replaced separately from the assembly. If the RDM motor is determined to be faulty in any way, the RDM assembly should be replaced.