Massey Ferguson 521010.05 – Engine Control Unit (ECU) / EEM4: DEF Tank Heater Coolant Valve Solenoid Low Side Open Circuit

The engine control module has detected an open circuit or a lower-than-expected current draw on the ground (low) side of the DEF tank heater coolant control valve solenoid. This valve controls the flow of warm engine coolant to the DEF tank to prevent the diesel exhaust fluid from freezing in cold weather. An open circuit usually points to a disconnected plug, a broken wire, or a failed solenoid coil.

• 7616
• 5612
• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 5611
• 7615
• 5610
• 5613
• 7620
• 5609
• 7618
• 5608
• 7619
• 7626
• 7624
• MF 4707
• MF 4708
• MF 4709
• MF 4710
• MF 5608
• MF 5609
• MF 5610
• MF 5611
• MF 5612
• MF 5613
• MF 5710 SL
• MF 5711 SL
• MF 5712 SL
• MF 5713 SL
• MF 7614
• MF 7615
• MF 7616
• MF 7618
• MF 7619
• MF 7620
• MF 7622
• MF 7624
• MF 7626
• MF 7714
• MF 7715
• MF 7716
• MF 7718
• MF 7719
• MF 7720
• MF 7722
• MF 7724
• MF 7726

1. 1

   Locate the DEF tank heater coolant valve and inspect the electrical connector for corrosion, pushed-out pins, or moisture ingress

2. 2

   Trace the wiring from the valve back to the Engine ECU and look for chafing, breaks, or rodent damage (most common cause of an open circuit)

3. 3

   Disconnect the valve and use a multimeter to measure the resistance across the solenoid coil pins (an infinite reading/OL confirms the solenoid coil has failed internally)

4. 4

   Turn the key ON and verify that the high side of the connector is receiving voltage and the low side has a proper path to ground when commanded by the ECU

1. 1

   Preparation

   Turn off the tractor, remove the key, and disconnect the negative battery terminal to prevent electrical shorts.

2. 2

   Access the Valve

   Locate the DEF tank heater coolant valve. If the engine is warm, allow the coolant to cool completely and relieve system pressure by slowly loosening the radiator cap.

3. 3

   Pinch Coolant Lines

   Clamp off the coolant hoses on both sides of the DEF heater control valve to minimize coolant loss.

4. 4

   Removal

   Disconnect the electrical harness from the solenoid. Loosen the hose clamps, pull the coolant lines off the valve, and remove the valve from its mounting bracket.

5. 5

   Installation

   Install the new DEF tank heater coolant valve. Reattach the coolant hoses and tighten the clamps.

6. 6

   Reconnect

   Plug the electrical connector back into the solenoid until it clicks. Remove the hose clamps.

7. 7

   Refill and Bleed

   Reconnect the battery. Top off the engine coolant if any was lost. Run the engine with the heater on to bleed any air pockets from the cooling system.

8. 8

   Clear Codes

   Use an AGCO EDT (Electronic Diagnostic Tool) or equivalent scanner to clear the 521010.05 fault code and verify it does not return.