Massey Ferguson 3363.03 – Engine ECU (AGCO SISU POWER EEM4): DEF Tank Heater Solenoid Valve High Voltage (ECU)

The DEF tank heater coolant valve is an electrically controlled solenoid valve that regulates the flow of warm engine coolant to a heating coil inside the DEF tank. The FMI 3 designation indicates that the controller has detected a voltage on this circuit that is above normal, meaning the circuit is shorted to a high voltage source (battery power) or has an open circuit/high resistance on the low side.

• 4710
• 7724S
• 5712SL
• Interim Tier 4 (2012-2015)
• 7722
• 7722S
• 7615
• 5613
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 7616
• 7618
• 5608
• 4708
• 7619
• 7626
• 7726S
• 7624
• 4707
• 4709
• 5711SL
• 7614
• 7718S
• 5610
• 7620
• 7719
• 7714
• 7716S
• T4 (2015-2021)
• 5612
• 7622
• 7720
• Tier 4 (2015-2021)
• 5611
• 7715S
• 5609
• 7724
• 5710 SL
• 5711 SL
• 5712 SL
• 5713 SL
• 9545
• 9565

1. 1

   Visually inspect the DEF tank heater coolant valve and the wiring harness between the Engine ECU and the valve for chafing, melted insulation, or exposed wires that could cause a short to battery voltage.

2. 2

   Disconnect the electrical connector at the solenoid valve and inspect the pins for corrosion, moisture intrusion, or damage.

3. 3

   Use a multimeter to measure the resistance of the DEF tank heater coolant valve solenoid to check for an internal short or open circuit.

4. 4

   Connect a diagnostic service tool, turn ignition ON (engine OFF), and perform an active command test to manually command the DEF coolant valve ON and OFF while monitoring circuit voltage to isolate the issue to the harness or the valve.

1. 1

   Turn off the ignition and disconnect the machine's battery to prevent electrical shorts during the repair.

2. 2

   If diagnostics point to a wiring issue, repair the shorted section of the harness between the ECU and the valve. If the valve itself has failed internally, proceed to replacement.

3. 3

   Clamp off the coolant supply and return lines on both sides of the DEF coolant valve using hose pinch pliers to minimize coolant loss.

4. 4

   Disconnect the electrical connector from the solenoid valve.

5. 5

   Loosen the hose clamps and carefully remove the coolant hoses from the valve.

6. 6

   Unbolt the faulty valve from its mounting bracket and remove it.

7. 7

   Install the new DEF tank heater coolant valve onto the bracket.

8. 8

   Reconnect the coolant hoses and securely tighten the hose clamps. Remove the hose pinch pliers.

9. 9

   Reconnect the electrical connector to the new valve.

10. 10

    Reconnect the battery and top off the engine coolant reservoir if any fluid was lost.

11. 11

    Connect a diagnostic tool, clear the active fault codes, and run a system test (commanding the valve open) to validate the repair.