New Holland NH 4172 – EHR Control Unit: EHR Control No.1 short circuit

The tractor's control system has detected a short circuit (either to ground or to a voltage source) in the electrical circuit for the Electronic Hydraulic Remote (EHR) control lever/potentiometer number 1.

• T-Series (T6, T7, T8, T9)
• T6000 Series (e.g., T6030, T6050)
• T7000 Series (e.g., T7030, T7060)
• TM Series (e.g., TM115, TM175, TM190)
• Genesis
• Versatile
• Buhler

1. 1

   Check the 5V Reference: Turn the key to the ON position and measure the voltage at the supply pins for the EHR lever connector. It should read approximately +5 Volts.

2. 2

   Check for a Short to Ground: With the key OFF, check the continuity between the signal pin on the lever connector and a known good ground.

3. 3

   Check for an Open Circuit: Disconnect the harness at both the EHR control unit and the armrest pod. Test the continuity of the wires end-to-end to ensure there are no breaks.

4. 4

   Test the Lever Potentiometer: Disconnect the EHR control unit connector. While physically moving the EHR No.1 lever from the 'extend' to 'float' positions, measure the resistance across the potentiometer pins (should show a smooth sweep between 100 Ohms and 900 Ohms).

1. 1

   Power Down

   Turn off the tractor and disconnect the battery to prevent electrical spikes during repair.

2. 2

   Harness Inspection & Repair

   If the diagnostic checks revealed a short to ground or voltage in the wiring, trace the EHR Control Valve Wire Harness from the armrest to the EHR controller. Look for pinch points, chafed insulation, or corroded connectors. Repair the damaged wires or replace the harness entirely.

3. 3

   Replace the EHR Control Pod

   If the wiring harness tests good, the short circuit is internal to the EHR lever's potentiometer. Remove the armrest console covers to access the EHR control pod. Disconnect the electrical connectors to the pod. Unbolt and remove the faulty EHR control pod (or the specific potentiometer switch if you are soldering in a component-level repair). Install the new control pod and reconnect the wiring.

4. 4

   Recalibration

   Reconnect the battery and turn the key ON. Note: Replacing the controller, pod, or valve will often trigger a subsequent fault code (NH 4170: 'EHR Control No. 1 not calibrated'). You must use the tractor's IntelliView display or enter the calibration menu to perform a spool travel calibration for the new remote valve lever.