Massey Ferguson E4340.05 – Engine Control Unit (ECU): DEF Suction Supply Pipe Heater Open Circuit

The control module has detected a break (open circuit) or infinite resistance in the electrical circuit that powers the heating element inside the DEF suction line (the hose carrying fluid from the DEF tank to the supply pump).

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

1. 1

   Inspect the DEF suction line electrical connector for disconnected plugs, corroded pins, or pushed-out terminals.

2. 2

   Trace the wiring harness from the ECU to the DEF suction line connector, checking for chafing, cuts, or breaks.

3. 3

   Perform a resistance test on the DEF suction line heater by disconnecting the connector and measuring resistance across the pins on the hose side. A reading of 'O.L' (infinite resistance) indicates a broken heating element.

4. 4

   Check the DEF suction line heater relay and associated fuses in the main fuse box to ensure power is being supplied to the circuit.

1. 1

   Preparation

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

2. 2

   Disconnect Electricals

   Unplug the electrical connector for the DEF suction line heater.

3. 3

   Disconnect Fluid Lines

   Locate the quick-connect fluid fittings at both ends of the suction line (one at the DEF tank, one at the DEF supply pump). Depress the release tabs and pull the fittings off. Note: Have a clean catch pan ready, as a small amount of DEF will spill.

4. 4

   Remove the Old Line

   Carefully unclip the line from its routing path. Note exactly how it is routed to avoid hot exhaust components and sharp edges.

5. 5

   Install the New Line

   Route the new heated DEF suction line exactly as the original was routed.

6. 6

   Reconnect Fittings

   Push the quick-connect fluid fittings onto the tank and pump nipples until they "click" and lock securely. (Failing to seat these properly will cause air ingress and subsequent DEF priming faults).

7. 7

   Reconnect Electricals

   Plug the new line's heater connector into the tractor's wiring harness.

8. 8

   Finalize

   Reconnect the battery. Use a diagnostic scan tool to clear the E4340.05 fault code. Turn the key on and run a DEF system test/prime sequence to ensure there are no leaks and the code does not return.