Massey Ferguson E4342.05 – Engine ECU: DEF Return Pipe Heater Open Circuit

The control module has detected a break in the electrical circuit (current below normal or infinite resistance) that powers the heating element inside the Diesel Exhaust Fluid (DEF) return 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

   Visually inspect the DEF Return Line Heater (DEFRLH) electrical connector and harness for damaged, corroded, or pinched wires, and loose, bent, or pushed-out pins.

2. 2

   Perform a resistance test across the pins of the DEF return line heater component. An open circuit (infinite resistance / OL) indicates the heating element inside the line has failed.

3. 3

   Perform a voltage test on the harness side by checking the DEF backflow line heater relay and fuses. Command the heater ON and measure voltage at the harness connector (should be battery voltage ± 0.5 volts). No voltage indicates a harness, relay, or ECU output issue.

1. 1

   Address Wiring (If Applicable)

   If the diagnostic checks reveal a harness issue, repair the broken wire or replace the damaged connector pigtail.

2. 2

   Depressurize and Clean

   If the heater element has failed, the entire DEF return line must be replaced. Clean the area around the DEF injector and the DEF supply module to prevent dirt from entering the SCR system.

3. 3

   Remove the Faulty Line

   Disconnect the AdBlue/DEF return line from the DEF injector and the DEF supply module. Note: Ensure that the open ports on the injector and pump are immediately capped/blocked to prevent debris entry.

4. 4

   Install the New Line

   Route the new DEF return line/heater assembly exactly as the old one was routed to prevent chafing or proximity to extreme exhaust heat. Click the fluid fittings securely into place.

5. 5

   Reconnect Electricals

   Plug the new heater's electrical connector into the engine harness.

6. 6

   Clear Codes

   Connect your electronic service tool (e.g., WinEEM4 or equivalent diagnostic scanner), clear the E4342.05 / SPN 4342 FMI 5 fault code, and cycle the key to verify the repair.