Massey Ferguson E4346.05 – ECU: DEF Injector Supply Heater Open Circuit (ECU)

The Engine Control Unit (ECU) has detected an 'open circuit' in the heating element of the Diesel Exhaust Fluid (DEF / AdBlue) injector supply line. An open circuit means there is infinite resistance, indicating a broken wire, a disconnected plug, or a burnt-out heater element inside the supply line.

• 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

   Visually inspect the DEF injector supply line (from pump module to doser/injector) for kinks, severe rub points, or physical damage.

2. 2

   Inspect the electrical connector where the heated line plugs into the main wiring harness for disconnected plugs, backed-out pins, or corrosion.

3. 3

   Perform a resistance test: disconnect the heater plug and use a multimeter to measure resistance across the heater element pins on the line side. If it reads 'OL' (Open Loop), the heating element is broken. If it reads normal resistance, the open circuit is likely in the tractor's wiring harness between the ECU and the plug.

1. 1

   Turn off the tractor, disconnect the battery, and ensure the exhaust system has cooled down.

   Safety precaution before beginning repair.

2. 2

   Clean the area around the DEF pump module and the DEF injector.

   Prevents dirt from entering the system, as tiny amounts of dirt can trigger 'poor DEF quality' codes.

3. 3

   Disconnect the electrical connector for the DEF injector supply heater.

4. 4

   Disconnect the quick-connect fittings at both ends of the DEF supply line (at the pump and at the injector).

   Be prepared to catch any residual DEF fluid.

5. 5

   Remove the old line.

   Note its exact routing for installation of the new line.

6. 6

   Install the new heated DEF supply line.

   Ensure it is routed away from hot exhaust edges and that the O-rings inside the quick connectors are seated properly to prevent air ingress and priming faults.

7. 7

   Reconnect the electrical plug for the heater.

8. 8

   Reconnect the battery, turn on the ignition, and use a diagnostic tool to clear the E4346.05 fault code from the ECU.

   Run the machine to verify the code does not return.