Drivetrain Control Module

WARNING: This page is about a different car, the 2021 Jeep Grand Cherokee L. However, it is still accessible from the selected car via links, so may be relevant.

DESCRIPTION

The Drivetrain Control Module (DTCM) is incorporated with the shift motor mounted to the transfer case. It communicates with the vehicle systems through the Controller Area Network - Flexible Data 3 (CAN-FD3) bus to optimize the performance of the vehicles 4 Wheel Drive (4WD) functionality.

The DTCM is powered by the front Power Distribution Center (PDC).

OPERATION

For 1 Speed & 2 Speed transfer cases, the DTCM has a direct mounted motor actuation system to modulate the clutch pack inside the transfer case. For the 2-Speed transfer case only, the DTCM also operates the Range Shift System. The DTCM also controls and operates the Front Axle Disconnect (FAD) during vehicle operation. Each DTCM is matched to a specific Transfer Case at the point of manufacturing which provides the most accurate torque delivery. Over time the clutch pack will wear. The DTCM adjusts for this clutch wear over the life of the vehicle.

POWER UP/DOWN

The DTCM will power up with an OFF to ON transition of the ignition input.

The DTCM will power down when the vehicle ignition transitions from ON to OFF if there are no system requirements that dictate the DTCM to remain active.

START-UP DIAGNOSTICS

When the DTCM is activated, the internal circuitry will undergo a diagnostic procedure. The DTCM will examine all inputs and outputs for short circuits to ground, short circuits to battery, open circuits, and will also verify proper Central Processing Unit (CPU) and memory operation. If a fault is detected, a message will be sent out over the CAN bus to the Instrument Panel Cluster (IPC) indicating that service is recommended.

After passing all diagnostic tests, the DTCM will continue to receive and process inputs, and produce the appropriate outputs while continuously monitoring system performance.

INPUTS/OUTPUTS

The following are inputs to the DTCM:

External Position Sensor (RPS) signal (2-Speed only)
Ignition RUN sense.
Front Axle Disconnect position feedback.
Range Switch.
Direct battery feed and DTCM ground.
CAN-FD3 bus messages.

The following are outputs of the DTCM:

Front Axle Disconnect - control & ground line.
Range shift control.
5V sensor supply.
Sensor ground.
CAN-FD3 bus messages.

TRANSFER CASE RANGE SELECT SWITCH INPUT (4WD NEUTRAL, and 4WD LOW)

With a two speed transfer case, the DTCM receives switch input from the vehicle CAN FD3 bus denoting the driver's selection to enter the 4WD-LOW or Neutral position. The one speed transfer case does not have range selection positions.

The driver can press and hold the 4WD Low switch to enter Low Range operation and exit Low Range operation to get back to Hi-Range operation.
The driver can press and hold the Neutral switch to shift the transfer case to Neutral Range and exit out of Neutral to Hi-Range operation.

The Transfer Case Switch Module (TCSM) is responsible for notifying the Body Control Module (BCM) of switched operation over the Local Interface Network (LIN) bus. The BCM communicates the switch position to the DTCM via the CAN-Interior High Speed (CAN-IHS) bus.

DTCM MODES OF OPERATION

NORMAL OPERATION

This mode is achieved when the ignition is in the RUN position. The DTCM powers up the FAD and 5V regulator circuit on the two speed transfer case. This mode also includes any required power-up system checks.

SHUT DOWN MODE

This mode is activated when the ignition is turned to the OFF position. The DTCM will perform any required shut down tasks prior to turning off the 5V regulator.

LIMP-IN MODE

This mode is entered when the DTCM has detected an error condition that prevents the system from performing its required task. The DTCM operation will vary from modified operation to total system shut down based on the failure that has occurred.