Case IH 3483 – Engine Control Unit (ECU): Coolant Pump PWM actuator: Open Load error on the output power stage

The Engine Control Unit (ECU) has detected an incomplete electrical circuit (an "open load") on the Pulse Width Modulation (PWM) control line that drives the engine coolant pump actuator. Because the circuit is broken or disconnected, the ECU cannot regulate the speed of the electrically controlled coolant pump, which can lead to improper engine cooling.

• Magnum
• Steiger
• Optum
• Puma

1. 1

   Visually inspect the wiring harness running from the Engine ECU to the Coolant Pump PWM Actuator for chafed wires, broken lines, or melted insulation.

2. 2

   Disconnect the plug at the coolant pump actuator and check for pushed-out pins, corrosion, or moisture inside the connector.

3. 3

   Use a multimeter to check the continuity of the power, ground, and PWM signal wires from the ECU harness to the actuator plug to rule out a broken wire (open circuit).

4. 4

   Measure the internal resistance of the Coolant Pump PWM Actuator itself. If the internal coil/circuit reads completely open (infinite resistance), the actuator has failed internally.

1. 1

   Safety First

   Turn off the machine, remove the key, and disconnect the negative battery cable. Ensure the engine is completely cool to avoid severe scalding from hot coolant.

2. 2

   Drain Coolant

   Slowly unscrew the radiator filler cap to release any residual pressure. Place a clean drain pan under the engine and drain the cooling system.

3. 3

   Remove the Actuator

   Locate the Coolant Pump PWM Actuator on the engine block (often integrated into or bolted directly to the mechanical coolant pump assembly). Disconnect the electrical harness.

4. 4

   Unbolt the Assembly

   Remove the mounting bolts securing the actuator/pump assembly to the engine block.

5. 5

   Install New Part

   Clean the mating surface on the engine block. Install the new Coolant Pump PWM Actuator using new OEM O-rings/seals to prevent leaks. Torque the mounting bolts to the manufacturer's specification.

6. 6

   Reconnect Wiring

   Plug the electrical connector back into the actuator, ensuring the locking tab clicks into place.

7. 7

   Refill and Bleed

   Refill the cooling system with the specified CNH/FPT approved coolant. Bleed any trapped air from the cooling system according to the engine's service manual.

8. 8

   Clear Codes

   Reconnect the battery, turn the key to the ON position, and use a diagnostic scan tool (such as the CNH Electronic Service Tool) to clear the 3483 fault code. Start the engine and verify there are no coolant leaks and that the code does not return.