New Holland 4121 – TCU: Open Circuit at Ride Control

The system has detected an open circuit at the ride control, indicating a break or disconnection in the electrical path. The ride control system cushions the loader arms to reduce bouncing and improve operator comfort. An open circuit prevents the system from being activated or deactivated because the electrical path to the controlling component, typically a solenoid or relay, is incomplete.

• W270B
• W110B
• W130B
• W170B
• W190B
• W270C
• L140
• L150
• L160
• L170
• L175
• L180
• L185
• L190
• C175
• C185
• C190
• T4 Series
• T5 Series

1. 1

   Visually inspect the wiring harness leading to the ride control solenoid and relay for chafed, broken, or disconnected wires, especially where the harness rubs against the frame.

2. 2

   Inspect electrical connectors at the ride control solenoid, relay, and TCU pins for corrosion, dirt, or bent/damaged pins.

3. 3

   Check the ride control relay by swapping it with a known good relay of the same type from another circuit on the machine.

4. 4

   Perform a solenoid resistance test by disconnecting the harness and measuring across the solenoid's terminals (expected resistance is 20 to 60 ohms; a reading approaching infinity indicates an open coil).

5. 5

   Perform a circuit continuity test with the key OFF by measuring resistance from the solenoid signal contact at the TCU connector to the solenoid connector, and check the ground return pin.

1. 1

   Repair harness or connectors

   If damaged wiring or a faulty connector is found during continuity testing or visual inspection, repair or replace the affected section of the harness. Ensure all connections are clean and secure.

2. 2

   Replace ride control relay

   If the ride control relay is determined to be faulty after swapping it with a known good unit, replace it with a new OEM or equivalent part.

3. 3

   Replace ride control solenoid

   If the solenoid coil has high resistance indicating an open circuit, ensure the hydraulic system is not under pressure. Disconnect the electrical connector, unscrew the solenoid from the hydraulic control valve body, and install a new solenoid ensuring seals/O-rings are correctly fitted.

4. 4

   Clear fault codes and verify

   After completing repairs, reconnect all components, start the machine, and clear the fault codes using the onboard diagnostic system or a service tool. Operate the ride control system to verify the fault does not return.