Massey Ferguson 4340.04 – Engine Control Unit (ECU): DEF Suction Supply Pipe Heater Resistance Is Low

The Engine Control Unit (ECU) has detected that the electrical resistance of the heater for the Diesel Exhaust Fluid (DEF) suction supply pipe is below the expected range. This condition suggests a potential short circuit in the heater element or its wiring, which can impair the system's ability to thaw frozen DEF in cold conditions and prevent proper dosing into the exhaust system.

• 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

1. 1

   Inspect the DEF suction supply pipe (the line running from the DEF tank to the DEF pump module) for physical damage, kinks, or rub points.

2. 2

   Disconnect the electrical connector for the DEF suction pipe heater and use a multimeter to measure the resistance across the heater element pins (near zero indicates an internal short).

3. 3

   Measure the resistance of the wiring harness leading back to the ECU to ensure the short is not in the tractor's main wiring harness.

4. 4

   Check the DEF suction line heater relay and associated fuses, as a shorted heater element will often blow the circuit protection.

1. 1

   Turn off the tractor ignition, remove the key, and disconnect the battery.

2. 2

   Thoroughly clean the exterior of the DEF tank header and the DEF pump module connections with warm water and a lint-free cloth.

   This prevents debris from entering the open ports.

3. 3

   Disconnect the electrical connector for the DEF suction supply pipe heater.

4. 4

   Depress the quick-release tabs on the fluid fittings to disconnect the suction pipe from the DEF tank and the dosing pump.

   Have a clean catch pan ready for minor fluid spillage.

5. 5

   Unclip the faulty heated line from its routing brackets and remove it from the tractor.

6. 6

   Route the new heated DEF suction pipe exactly as the old one was routed.

   Ensure it is secured away from sharp edges, moving parts, and hot exhaust components.

7. 7

   Push the quick-connect fluid fittings onto the ports until they click securely into place.

   Ensure the internal O-rings are not nicked or pinched.

8. 8

   Reconnect the electrical connector for the heater.

9. 9

   Reconnect the battery, turn the ignition on, and use a diagnostic service tool or the tractor's diagnostic dashboard menu to clear the stored 004340.04 fault code.

10. 10

    Run the tractor to verify that the code does not return and inspect the quick-connect fittings for any DEF leaks.