CACM : HCM Communication Error

Insert a software upgrade token into the ADM and cycle the power.  Make certain to wait until the upload is complete before removing the token.  For more information on loading software, refer to the module programming manual by searching for "3A1244" at

Ensure the HCM dial is set to the correct position.

  • H-30: dial position = 0
  • H-40: dial position = 1
  • H-50: dial position = 2
  • H-XP2: dial position = 3
  • H-XP3: dial position = 4
  • Green light on each module should be lit.  If green light is not lit, check to make sure each CAN cable connection is not cross threaded and is tight.
  • Verify the power supply is outputting 24 V dc.  If not, check power supply wiring.  If wiring is okay, replace the power supply.

Check the CAN cables running between GCA modules.  Check for cross threading and tighten if needed.  If the problem still persists, grasp the cable near the connector, move it around, and watch the flashing yellow light on the GCA modules.  If the yellow light stops flashing, replace the CAN cable.