Case IH 3477 – Engine Control Unit (ECU / EDC): Coolant Pump speed: pump speed too high

This fault code indicates that the measured rotational speed of the engine's electrically controlled coolant pump is excessive. The underlying condition is typically caused by a defective coolant pump speed sensor reporting an incorrect (too high) value, or the pump being physically switched into a higher speed stage than the one currently commanded and detected by the control unit.

• Farmall
• Maxxum
• Puma
• Magnum
• Steiger

1. 1

   Check the coolant pump speed sensor for physical damage, corrosion, or debris.

2. 2

   Inspect the CAN cable connecting the Water Pump Controller (WPC) to the Engine ECU for disconnected, broken, or short-circuited wiring.

3. 3

   Verify the operation of the pump stage switch to ensure it is not mechanically stuck in a high-speed position.

4. 4

   Check for high resistance in the sensor wiring harness or abnormal voltage drops that could skew the sensor's reading.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the battery to prevent electrical shorts.

2. 2

   Inspect and Clean

   Locate the coolant pump speed sensor on the water pump assembly. Disconnect the harness and clean the contacts.

3. 3

   Replace the Speed Sensor

   If diagnostic testing confirms the sensor is outputting an out-of-range signal, remove the retaining bolt, pull the old sensor, and install a new speed sensor.

4. 4

   Check the Pump Module

   If the sensor is functioning correctly but the fault persists, the internal controller of the water pump (WPC) or the pump motor itself is likely defective.

5. 5

   Replace the Coolant Pump

   Drain the engine coolant. Disconnect the coolant hoses and the electrical harness from the pump module. Unbolt the pump from the engine block, clean the mating surface, and install the new coolant pump with a new gasket.

6. 6

   Refill and Clear Codes

   Refill the system with the specified coolant, reconnect the battery, and use a diagnostic tool to clear the fault code. Run the engine to verify the pump operates at the commanded speed without throwing a code.