Theory Of Operation
Active Transfer Case (DHP and DHF) - Shift Motor Position Sensing
The Transfer Case Shift Motor is equipped with magnets on the armature that rotate past two hall effect sensors when the motor is turning. The Drivetrain Control Module (DTCM) counts the pulses in order to determine the relative position of the Front Drive Clutch (2WD, 4WD, and 4WD-AUTO modes) inside the Transfer Case.
There are 4 Hall-Effect Sensor related circuits between the Shift Motor and the DTCM:
- 5-Volt Supply
- Sensor Ground
- Hall-Effect Sensor A Signal
- Hall-Effect Sensor B Signal
Each sensor creates a square wave signal that is slightly offset from one another. This allows the DTCM to determine which direction the motor is turning. If the DTCM determines that some of the square wave pulses are missing, a DTC will be set. Once the fault condition is corrected, a Non-Volatile Memory Reset (Clear T-Case Adaptives) with the scan tool is required to relearn the motor positions.