Massey Ferguson E4354.04 – Engine Control Unit (ECU) / AGCO SISU POWER EEM4: DEF Suction Supply Pipe Heater Relay Issue

The system has detected a "Voltage Below Normal, Short to Ground, or Open Circuit" on the high side of the DEF suction line heater relay (Line Heater 1). This means the electrical circuit responsible for turning on the heater for the DEF suction line is compromised.

• 7616
• 5612
• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 5611
• 7615
• 5610
• 5613
• 7620
• 5609
• 7618
• 5608
• 7619
• 7626
• 7624
• MF 5608
• MF 5609
• MF 5610
• MF 5611
• MF 5612
• MF 5613
• MF 7614
• MF 7615
• MF 7616
• MF 7618
• MF 7619
• MF 7620
• MF 7622
• MF 7624
• MF 7626

1. 1

   Locate the Power Distribution Unit (PDU) / fuse box and identify the DEF Suction Line Heater Relay (often labeled as Line Heater 1).

2. 2

   Inspect the relay for internal failure (open coil) and inspect the socket for melted plastic, pushed-out pins, or green corrosion.

3. 3

   Use a multimeter to verify that the relay socket is receiving 12V power from the battery/fuse panel.

4. 4

   Disconnect the harness at the DEF suction line heater and at the relay. Test the wiring for continuity (to find broken wires) and test for continuity to ground (to find chafed wires shorting against the tractor frame).

5. 5

   Inspect connectors for broken wires located within a foot of the connectors or hidden inside the factory heat shrink.

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the negative battery cable to protect the ECU.

2. 2

   Test/Replace the Relay

   Swap the DEF Suction Line Heater Relay with a known good relay of the exact same type (e.g., a work light relay). If the code changes or clears, the relay is the culprit and must be replaced.

3. 3

   Repair Wiring (If Relay is Good)

   If the relay is functional, trace the wiring harness from the PDU down to the DEF suction line heater.

4. 4

   Fix Breaks

   Carefully slice open the protective wire loom at sharp bends or areas where the harness rubs against the chassis. If a broken or shorted wire is found, cut out the damaged section and repair it using weather-resistant, heat-shrink butt connectors.

5. 5

   Reassemble

   Re-loom the wiring and secure it with zip ties, ensuring it is routed away from high-heat or high-friction areas.

6. 6

   Clear Codes

   Reconnect the battery. Use an AGCO diagnostic service tool (or equivalent heavy-duty scanner) to clear the E4354.04 / SPN 4354 FMI 4 fault code.

7. 7

   Verify

   Cycle the key and run a system test to ensure the ECU can successfully command the DEF heater relay without detecting a short or open circuit.