New Holland 4191 – ARU: No Communication from EHR No. 2

The Armrest Control Unit (ARU) has lost CAN bus communication with the number 2 Electro-Hydraulic Remote (EHR) valve controller. The main control unit is not receiving any signal from the electronic module that controls the second hydraulic remote valve, indicating a failure in the communication link, wiring harness, or the EHR component itself.

• T6000
• T7000
• T7
• T8
• T9

1. 1

   Visually inspect the wiring harness leading to the rear hydraulic remote valves, specifically the EHR No. 2 valve stack, for chafing, cuts, or corrosion.

2. 2

   Verify that the EHR No. 2 module is receiving the correct voltage and has a solid ground connection.

3. 3

   Perform a CAN bus integrity check with power off: measure resistance between CAN high and CAN low at a known good point in the harness, such as the diagnostic connector. A healthy CAN bus should have a resistance of approximately 60 ohms. A reading of 120 ohms indicates a missing terminating resistor, while a reading significantly lower than 60 ohms could indicate a short in the wiring or a faulty module.

4. 4

   Check CAN bus voltages with the key on: CAN high should be 2.5-3.0 volts, and CAN low should be 2.0-2.5 volts.

5. 5

   Isolate the faulty module by disconnecting the EHR No. 2 module to see if communication with other modules on the bus is restored.

1. 1

   Repair wiring

   If damage is found during inspection, repair broken wires, replace damaged connectors, or reroute the harness to manufacturer specifications to prevent future damage.

2. 2

   Clean connectors

   Thoroughly clean any corroded connectors with electrical contact cleaner and ensure a secure connection when reconnecting.

3. 3

   Replace EHR No. 2 module

   If diagnostic checks point to a faulty module, replace the Electro-Hydraulic Remote Valve No. 2 located on the rear hydraulic remote valve stack.

4. 4

   Calibrate new module

   Use the tractor's diagnostic interface or a specialized service tool to calibrate the new EHR module and teach the main controller its operational parameters.