Test C: Four Wheel Drive (4WD) Control Module Received No/Invalid Data From PCM

Pinpoint Test C: Four Wheel Drive (4WD) Control Module Received No/Invalid Data From PCM
Refer to Vehicle/Diagrams, Four Wheel Drive (4WD) Systems for schematic and connector information.

Normal Operation
The on-demand four wheel drive (4WD) system uses data from other systems as inputs to the 4WD control module. The 4WD control module uses the inputs to determine the appropriate duty cycle to send to the active torque coupling that delivers the desired torque to the rear wheels. Specific inputs to the 4WD control module are: accelerator pedal position output from the PCM, transmission range from the PCM, brake system status and all 4 wheel speeds from the ABS module. Communication between the 4WD control module and other modules is obtained through the high-speed controller area network (HS-CAN). If the 4WD control module loses communication with, or receives invalid data from any of the necessary modules, DTCs are set and the 4WD control module may not allow 4WD operation.
^ DTC U0401 Invalid Data Received from PCM -When the 4WD control module receives invalid HS-CAN bus message for more than 30 seconds from the PCM, this DTC is set.

This pinpoint test is intended to diagnose the following:
^ PCM

C1: