Description And Operation

DESCRIPTION 

Courtesy of CHRYSLER GROUP, LLC

The Drivetrain Control Module (DTCM) (1) is located in the instrument panel. It communicates with the vehicle systems through the Controller Area Network (CAN)-C bus to optimize the performance of the vehicles All Wheel Drive (AWD) functionality.

The AWD system incorporates driveline (rear axle) disconnect technology, anticipator launch capability, and infinitely variable torque (e.g. front/rear torque split) and optimizes traction on all surfaces, and in all dynamic scenarios.

The DTCM is located in the passenger footwell, below the Heating, Ventilation and Air Conditioning (HVAC) blower.

OPERATION 

Courtesy of CHRYSLER GROUP, LLC

• The AWD system requires no driver input or control.
• Under most driving conditions, it is passive and power is transmitted to the front wheels alone.

The system functions to optimize traction and handling:

• Anticipates slip by responding to pedal position.
• The system requires no front-to-rear slippage for activation.
• Allows the system to transfer torque in response to accelerator pedal position.
• Once a demand for power is signaled, the system immediately starts clamping the Rear Drive Unit (RDU) and transferring a high percentage of power to the rear wheels.
• Modulates torque to optimize traction on slippery surfaces.
• Avoids front wheel slippage, as power to propel the car is transmitted through all four tires.
• The mode of operation is called open-loop operation in that there is no feedback to affect the torque transfer.
• A second, closed loop, operating mode uses feedback from the wheel-speed sensors to determine the appropriate torque transfer.
• When the front wheels slip, the DTCM tells the RDU to start clamping, sending power to the rear wheels.
• With the front wheels on ice and the rear wheels on dry pavement, the RDU sends even more torque to the rear wheels to minimize slippage and launch the vehicle.
• Both modes are always active and the maximum of the two is chosen.
• Influences handling at moderate speeds.
• The AWD system is used to influence vehicle dynamics.
• Additional Powertrain Control Module (PCM) calibration controls torque to the rear wheels for improved handling.
• The control strategy provides minimal torque to the rear wheels under normal driving conditions to aid fuel economy.
• The system utilizes torque to the rear wheels during cornering with the throttle open to make the handling more neutral.
• The AWD system uses the Electric Power Steering (EPS) steering angle sensor to determine when the vehicle is turning in a tight circle.
• Prevents binding during low-speed turns. DTCM to reduce amount of torque to the rear wheels to prevent binding in the driveline. The DTCM is always checking for this condition.
• The DTCM also interfaces with the Electronic Stability Program (ESP) and traction control systems.
• The interface allows the ESP system to use the RDU to help gain control of the vehicle.
• Torque transmitted to the rear wheels by the RDU can be reduced.
• Power to the rear wheels is modulated during loss of traction while traveling at freeway speeds such as, hydroplaning on a puddle of water, will send very little power to the rear wheels.
• The AWD system is not traction control and only works on situations where front-to-rear traction varies.
• AWD does not aid side-to-side traction; the ESP does that through brake intervention.