Case IH 19877 – Dosing Control Unit (DCU): DEF/AdBlue supply module pump motor pressure is too high.

This code indicates that the pressure generated by the Diesel Exhaust Fluid (DEF) pump has exceeded the normal operating threshold. This is typically caused by a blockage in the DEF lines (dead-heading), a clogged DEF dosing valve (injector) due to crystallization, a restricted return line, or an internal failure of the DEF supply module itself.

• Tier 4b
• Magnum (180-400)
• Steiger (350-620)
• Puma (130-240)
• Maxxum (110-150)
• Optum (270-300)
• Combines 5130-9260 series
• Patriot
• Trident
• Titan

1. 1

   Inspect the DEF supply and return lines for kinks, pinches, or physical damage (diagnosing a blocked return line causing pressure to spike).

2. 2

   Remove the DEF dosing valve (injector) from the exhaust stream and inspect it for severe urea crystallization or white crust (diagnosing a blocked injector causing the pump to dead-head).

3. 3

   Check the main DEF filter inside the DEF supply module for severe contamination or blockages.

4. 4

   Use the CNH Electronic Service Tool (EST) to run a DEF system pressure test and monitor the pressure sensor readings (diagnosing if the pressure is actually high or if the sensor is reading erratically).

1. 1

   Preparation

   Turn off the machine and wait at least 5-10 minutes for the ACM to complete its purge cycle (pumping DEF back into the tank). Clean the area around the DEF supply module thoroughly to prevent dirt from entering the SCR system.

2. 2

   Disconnect Electricals

   Unplug the main electrical harness connector from the DEF pump.

3. 3

   Disconnect Fluid Lines

   Disconnect the DEF supply, DEF return, and engine coolant lines (which heat the pump). Note: Have a catch pan ready. Clean up any spilled DEF immediately using warm, distilled water to prevent corrosion.

4. 4

   Remove the Module

   Remove the mounting bolts securing the DEF supply module to the chassis/bracket and remove the unit.

5. 5

   Install the New Module

   Mount the new DEF supply module and tighten the bolts to OEM torque specs.

6. 6

   Reconnect Lines

   Reconnect the coolant lines and the DEF supply/return lines. Ensure the fittings click securely into place. Reconnect the electrical harness.

7. 7

   Prime and Program

   Connect the CNH EST diagnostic tool. You must program/calibrate the new module to the vehicle's ECU. Run a system prime and a dosing system test to verify that the pump builds and maintains normal operating pressure (typically around 9 bar / 130 psi for Bosch Denoxtronic systems).

8. 8

   Clear Codes

   Clear fault code 19877 and verify that the engine derate is lifted.