Massey Ferguson 4354.04 – Engine ECU: DEF Suction Supply Pipe Heater Relay Issue (ECU)

The engine control system has detected an open circuit on the high side of the relay responsible for powering the heater in the Diesel Exhaust Fluid (DEF) suction line.

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

1. 1

   Check fuses dedicated to the DEF/AdBlue heating system and the ECU main power for a blown fuse

2. 2

   Inspect the DEF suction line heater relay terminals for corrosion, pushed-out pins, or signs of overheating. Swap with a known good relay to test

3. 3

   Trace the wiring harness from the ECU to the DEF suction line heater relay, and from the relay to the DEF suction line, looking for chafed wires, broken connections, or corrosion

4. 4

   Disconnect the DEF suction line and use a multimeter to check the resistance (continuity) of the heater element inside the line

1. 1

   Disconnect Power

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

2. 2

   Repair Wiring

   If a broken wire or corroded connector was found during the diagnostic phase, cut out the damaged section and splice in new wiring using weather-sealed heat-shrink butt connectors.

3. 3

   Replace the Relay

   If the wiring is intact but the relay failed the swap test, remove the faulty DEF suction line heater relay from the fuse/relay panel and install a new OEM relay.

4. 4

   Replace the DEF Suction Line

   If the heater element inside the suction line is burnt out (open circuit), disconnect the quick-connect fittings at the DEF tank and the pump module. Remove the old line and route the new heated line, ensuring it is kept away from sharp edges or extreme heat sources to prevent future chafing.

5. 5

   Clear Codes

   Reconnect the battery. Use a diagnostic service tool (like the WinEEM4 Service Tool) to save the error log and then erase the fault codes.

6. 6

   Test Operation

   Restart the ECU/tractor and monitor the system to ensure the fault code does not return and that the engine does not enter a derate condition.