New Holland NH 4190 – Armrest Module (ARU) or Tractor Control Unit (TCU) / Main Vehicle Controller: No communications from (EHR) No.1

The main vehicle controller has completely lost CAN bus communication with the #1 Electro-Hydraulic Remote (EHR) valve module.

• T7 Series (e.g., T7.220, T7.235, T7.270, T7.275 Auto Command)
• T8 Series (e.g., T8.275, T8.300, T8.390)
• T9 Series
• TM Series (e.g., TM175, TM190)

1. 1

   Check System-Wide Communication: Verify if fault codes 4191, 4192, or 4193 are also active. If multiple EHR valves are offline, the issue is likely a main CAN bus failure, a severed main harness, or an Armrest Controller (ARU) issue.

2. 2

   Inspect the Wiring Harness: Check the CAN bus wiring harness leading directly to the EHR No.1 valve for chafing, open circuits, or short circuits.

3. 3

   Check Power and Ground: Ensure the EHR No.1 valve is receiving proper supply voltage (12V) and has a clean ground connection.

4. 4

   Inspect Connectors: Disconnect the EHR No.1 harness and check for bent pins, pushed-out terminals, water intrusion, or corrosion.

1. 1

   Disconnect Power

   Disconnect the tractor's battery before servicing the CAN bus or hydraulic electrical components.

2. 2

   Repair Wiring

   If the diagnostic checks reveal a broken wire or corroded connector at the No.1 valve, repair the wiring harness or replace the EHR pigtail harness.

3. 3

   Replace the EHR Valve

   If the wiring, power, and ground are all intact, the internal processor inside the EHR No.1 valve has failed. The valve assembly must be replaced.

4. 4

   Reassemble and Power Up

   Install the new EHR valve, reconnect the hydraulic lines, and plug in the CAN bus connector. Reconnect the battery.

5. 5

   Calibrate the New Valve

   A newly installed EHR valve must be calibrated so the main controller can recognize its position on the CAN bus and learn the spool travel limits. This is done via the tractor's instrument cluster 'H-Menu' or by using the CNH Electronic Service Tool (EST).