Case IH 3486 – Engine Control Module (ECM): Engine coolant pump actuator PWM power stage: short to ground.

The Engine Control Module (ECM) uses a Pulse Width Modulation (PWM) signal to control the engagement of the variable-speed/viscous engine coolant pump. This code indicates that the ECM has detected a short circuit to ground on the PWM control circuit. Because the power stage is shorted to ground, the ECM cannot regulate the water pump speed, causing it to default to a mechanical fail-safe (usually 100% lockup/maximum speed) to prevent engine overheating, or it may fail to circulate coolant adequately.

• Puma 150
• Puma 165
• Puma 185
• Puma 200
• Puma 220
• Puma 240
• Magnum 235
• Magnum 250
• Magnum 260
• Magnum 280
• Magnum 310
• Magnum 340
• Magnum 380
• Optum
• Steiger
• Axial-Flow 5130
• Axial-Flow 6130
• Axial-Flow 7130
• Axial-Flow 6140
• Axial-Flow 7140
• Patriot 3230
• Patriot 3330
• Patriot 4430

1. 1

   Harness Inspection: Visually inspect the engine wiring harness from the ECM to the coolant pump actuator. Look for chafed insulation, melted wires, or pinch points against the engine block or brackets.

2. 2

   Continuity to Ground Test: Disconnect the electrical connector at the water pump actuator. Using a multimeter, test the PWM signal wire on the harness side for continuity to ground. If continuity exists, the harness is shorted and must be repaired.

3. 3

   Actuator Internal Short Test: Test the resistance across the pins on the water pump actuator itself, and test each pin for continuity to the pump housing (ground). If the actuator is internally shorted to its housing, the pump assembly must be replaced.

4. 4

   Connector Check: Inspect the actuator connector for water intrusion, corrosion, or bent pins which can bridge the circuit to ground.

1. 1

   Preparation

   Turn off the master battery disconnect switch. Ensure the engine is completely cool.

2. 2

   Drain Coolant

   Place a clean drain pan under the radiator/engine block and drain the engine coolant.

3. 3

   Remove Belt

   Use a breaker bar or the appropriate tensioner tool to release tension on the serpentine belt. Slip the belt off the water pump pulley.

4. 4

   Disconnect Wiring

   Unplug the electrical connector from the water pump PWM actuator.

5. 5

   Remove Pump

   Remove the mounting bolts securing the water pump assembly to the engine block. Carefully remove the pump.

6. 6

   Clean Surface

   Thoroughly clean the mounting surface on the engine block, ensuring no old gasket material or debris remains.

7. 7

   Install New Pump

   Install the new water pump assembly using a new O-ring/gasket. Hand-thread the mounting bolts, then torque them to the OEM specification in a crisscross pattern.

8. 8

   Reassembly

   Reinstall the serpentine belt and reconnect the PWM actuator electrical connector.

9. 9

   Refill and Test

   Refill the cooling system with the specified Case IH Actullaction/OAT coolant. Turn on the battery, connect the Electronic Service Tool (EST) to clear the fault code, and run the engine. Verify that the code does not return and check for coolant leaks.