Massey Ferguson U 700 – Engine Control Unit (ECU) or Aftertreatment Control Module (ACM): Heating supply of the pressure pipeline

Electrical malfunction in the heating element of the DEF (Diesel Exhaust Fluid) / AdBlue pressure line.

• MF 8600 Series
• MF 7600 Series
• MF 5S Series

1. 1

   Inspect the DEF pressure line (running from the pump to the injector) for physical damage, kinks, or severe rubbing against the chassis, which could sever the internal heating wire.

2. 2

   Check the electrical connector for the pressure line heater for corrosion, moisture, or loose pins.

3. 3

   Use a multimeter to test the resistance of the heating element inside the DEF line. An infinite reading confirms an 'Open load' (FMI 5), meaning the line must be replaced. A zero reading indicates a short circuit.

4. 4

   Check the SCR system fuses and the pressure line heater relay in the fuse box to ensure a blown fuse isn't causing a false open circuit reading.

5. 5

   Inspect the DEF tank and line fittings for crystallized DEF, which can cause blockages or leaks.

1. 1

   Preparation

   Park the tractor on a level surface, turn off the engine, and disconnect the battery to prevent electrical shorts.

2. 2

   Locate Components

   Locate the DEF supply module (pump) and trace the heated pressure line to the DEF dosing injector on the exhaust/SCR catalyst.

3. 3

   Disconnect Electricals

   Disconnect the electrical pigtail connector for the DEF pressure line heater.

4. 4

   Disconnect Fluid Lines

   Carefully disconnect the quick-connect fluid fittings at both ends of the pressure line. Clean any crystallized DEF from the module and injector fittings using warm water before installing the new line.

5. 5

   Remove the Line

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

6. 6

   Route the New Line

   Route the new DEF heated pressure line exactly as the original. Ensure it is insulated, secured in its clips, and kept away from sharp edges and extreme exhaust heat sources to prevent future melting or rubbing.

7. 7

   Reconnect

   Snap the quick-connect fluid fittings onto the pump and injector until they click securely. Reconnect the heater's electrical connector.

8. 8

   Clear Codes

   Reconnect the battery. Turn on the ignition and use a dealer diagnostic tool to clear the U 700 fault code.

9. 9

   Test

   Start the engine and allow it to reach operating temperature. Verify that the SCR system functions correctly, the heater activates without throwing a code, and there are no fluid leaks.