Case IH 4004 – Armrest Control Module (ACM): ACM (GARU) Offline

Communication has been lost with the Armrest Control Module (ACM). The system has detected that the module is no longer communicating on the CAN bus network.

• Magnum
• Steiger T4B
• Case IH Magnum Series: 235 - 340 (Series 4)
• Case IH AFS Connect Magnum Series: 180, 200, 220, 240, 250, 280, 310, 340, 380
• Case IH Steiger / Quadtrac Series

1. 1

   Check for related codes: Use the Electronic Service Tool (EST) or the cab display to check for any other Armrest Control Module (ACM) error codes.

2. 2

   Clear and Retest: Make a note of all active and stored error codes, clear them from the system, and test the tractor's hydraulic and armrest functions for normal operation.

3. 3

   Inspect Wiring: If the fault returns, physically check all connectors and wiring harnesses leading to the Armrest Control Module and the EHR valve sections for corrosion, backed-out pins, or damage.

4. 4

   CAN Bus Check: Verify the CAN bus integrity and check the controller status using the EST to ensure the module is receiving power and ground.

1. 1

   Power Down

   Turn off the tractor and disconnect the battery before servicing electrical components.

2. 2

   Inspect and Clean Connectors

   Locate the ACM (typically inside the armrest console) and the EHR valve sections (at the rear remotes). Disconnect the harnesses, inspect for moisture or pin damage, clean with contact cleaner, and apply dielectric grease.

3. 3

   Test Operation

   Reconnect the battery, power up the tractor, and check if the 4004 code clears.

4. 4

   Isolate the EHR Valves

   Because a shorted EHR valve section can pull the ACM offline, disconnect the EHR valves one by one to see if communication to the ACM is restored. If the code changes or communication returns when a specific valve is unplugged, that EHR valve section/pilot head is the culprit.

5. 5

   Replace Faulty Component

   If the wiring is intact and isolating the EHR valves does not restore communication, the Armrest Control Module (ACM) itself has likely failed internally and must be replaced.

6. 6

   Recalibrate

   If the ACM or an EHR valve is replaced, you must use the EST to flash the correct software dataset and recalibrate the armrest levers and hydraulic flow settings.