New Holland NH 4191 – Main Vehicle Controller: No communications from (EHR) No.2.

This fault code indicates that the tractor's main control system has lost CAN bus communication with the Electro-Hydraulic Remote (EHR) valve number 2. The EHR valve has an integrated electronic module that must continuously broadcast its status to the network; when these messages stop, the system flags the valve as offline.

• New Holland T6 Series
• New Holland T7 Series
• New Holland T8 Series
• New Holland T9 Series
• New Holland TG Series
• New Holland TM Series
• New Holland 8000 Series (e.g., 8670, 8770, 8870, 8970)

1. 1

   Visual Inspection: Inspect the electrical connector at the EHR No.2 valve slice at the rear of the tractor. Look for water intrusion, corrosion, or pushed-back pins.

2. 2

   CAN Bus Resistance Test: Turn the key off. Disconnect the EHR No.2 valve connector. Using a multimeter, check the resistance of the CAN wiring between terminals 2 and 3 (typically the green and yellow wires). The resistance should be approximately 120Ω. If it reads 'Open' or significantly higher/lower, there is a wiring harness failure.

3. 3

   Power and Ground Check: Verify that the EHR No.2 valve is receiving unswitched battery power, switched ignition power, and a solid ground.

4. 4

   Component Swap Test: To isolate whether the issue is the valve's internal module or the tractor's wiring, swap the electrical connection of EHR No.2 with a known good valve (such as EHR No.1 or No.3). If the fault code changes to the new position (e.g., NH 4192 for EHR No.3), the wiring is bad. If the fault remains NH 4191, the EHR No.2 valve module has failed internally.

1. 1

   Harness Repair (If applicable)

   If the CAN resistance test failed, trace the wiring harness from the rear remotes back to the main controller. Repair any broken wires or replace damaged connectors.

2. 2

   Valve Replacement (If the valve is faulty)

   Relieve all hydraulic pressure from the system. Clean the area around the rear remote valve stack to prevent dirt from entering the hydraulic system. Disconnect the electrical connector from the EHR No.2 valve. Unbolt the tie-rods/mounting bolts holding the valve stack together and carefully remove the faulty EHR No.2 slice. Install the new EHR valve section, ensuring all O-rings between the valve slices are properly seated and lubricated. Torque the valve stack bolts to OEM specifications and reconnect the electrical harness.

3. 3

   Software & Calibration

   Turn the key on and use a New Holland diagnostic tool (such as the CNH EST or Jaltest) to clear the inactive fault codes. Depending on the tractor model, you may need to reload the software into the XCM processor so it recognizes the new valve. Perform the EHR valve spool calibration procedure via the diagnostic tool or the tractor's in-cab display to set the neutral, extend, and retract limits.