Case IH 17753 (F-6875-15) - ECU – Engine Control Unit (ECU): DEF/AdBlue supply module UREA pressure sensor value is too high

The engine's control system has detected that the fluid pressure inside the Selective Catalytic Reduction (SCR) DEF dosing system exceeds normal operating limits. This condition is typically caused by a physical blockage in the DEF delivery lines, a clogged dosing injector nozzle (often due to crystallized urea), or a failure of the pressure sensor itself, which is integrated internally within the DEF supply module.

• VESTRUM CVX
• Austoft 9900 sugarcane harvesters
• Steiger series tractors
• Magnum series tractors
• Puma series tractors
• Patriot series sprayers

1. 1

   Inspect the DEF tank for old, contaminated, or crystallized fluid, which is the leading cause of SCR system blockages.

2. 2

   Inspect the DEF supply lines between the supply module (pump) and the dosing injector for kinks, damage, or severe crystallization.

3. 3

   Connect the Case IH Electronic Service Tool (EST) and run a Urea Dosing System Test (UDST).

4. 4

   Verify pressures during the UDST: active system pressure should be 4900 to 6200 millibar (71.1 to 89.9 psi). During the evacuation/purge cycle, the pressure should drop to between -50 and -300 millibar (-0.72 and -4.35 psi).

5. 5

   Check the DEF supply module's internal primary filter for heavy urea sediment or micro-contaminants.

1. 1

   Turn off the machine and disconnect the battery

   This prevents electrical shorts during the repair.

2. 2

   Depressurize and drain the DEF system

   Perform this step if the lines are heavily contaminated.

3. 3

   Disconnect and flush the DEF lines

   Disconnect the DEF lines at the supply module and the dosing injector. Flush the lines with warm distilled water to dissolve any crystallized urea blockages. If a line is completely obstructed and cannot be cleared, replace it.

4. 4

   Replace the DEF supply module main filter element

   Remove and replace the internal primary filter element.

5. 5

   Replace the DEF supply module/pump assembly

   If the lines and injector are clear but the pressure reading remains implausibly high (or fails the UDST pressure test), the internal pressure sensor has failed. Because the sensor is integrated, the entire DEF supply module/pump assembly must be replaced.

6. 6

   Install the new DEF supply module

   Reconnect all fluid lines and electrical harnesses to the new module.

7. 7

   Reconnect the battery

   Restore power to the machine.

8. 8

   Clear fault codes and run a forced dosing test

   Use the EST to clear the fault codes, then run a forced dosing test to prime the system and verify that the operating pressure stabilizes within the 4900–6200 millibar specification.