Massey Ferguson U 1387 – SCR (Selective Catalytic Reduction) system / Dosing Control Unit (DCU) or Engine ECU: Urea pressure sensor plausibility error: Dynamic plausibility / Urea pressure monitoring: Pressure too low

The system is detecting that the pressure of the Diesel Exhaust Fluid (DEF/AdBlue) is either too low to operate the emissions system correctly or the sensor's readings are dynamically implausible (erratic or not matching expected values during operation).

• Massey Ferguson 8600 Series
• Massey Ferguson 8660
• Massey Ferguson 8670
• Massey Ferguson 8680
• Massey Ferguson 8690
• Massey Ferguson 6700 S Series

1. 1

   Inspect the urea pressure sensor harness and power supply circuit for a short circuit to Battery+ or Ground, or supply voltage out of limits.

2. 2

   Inspect the heated DEF lines (supply and return) for leaks, kinks, rub points, or nicks in the O-rings and quick connectors that could allow air ingress.

3. 3

   Check the DEF tank cap and breather for dirt or moisture ingress, and ensure there is no crystallized urea blocking the lines, the pump's fine filter/strainer, or the injector.

4. 4

   Verify if the pump module is drawing DEF properly, pressurizing the system, and reversing briefly at shutdown to purge fluid back to the tank.

1. 1

   Clean the Area

   Before opening any part of the DEF system, thoroughly clean the tank neck and surrounding components to prevent dirt from entering the system.

2. 2

   Repair Wiring (If Applicable)

   If diagnostic checks reveal a voltage issue, repair the urea fluid sensor power supply circuit or replace the damaged console harness.

3. 3

   Replace the DEF Filter

   If the system is struggling to build pressure, remove and replace the DEF pump filter/strainer, as a clogged filter will restrict flow.

4. 4

   Replace the Sensor/Pump Module

   If the wiring is intact, there are no leaks, and the filter is clean, the urea pressure sensor or the pump itself has failed. On these systems, the pressure sensor is often integrated into the DEF Supply Pump Module. Replace the faulty sensor or the entire pump module.

5. 5

   Clear Codes and Test

   Use a diagnostic scan tool to clear the U 1387 code. Start the engine and monitor the DEF pressure dynamically to ensure the new components are registering plausible pressure values.