Case IH 19999 – DCU (Dosing Control Unit): Unknown DCU15 fault code

This code is a generic placeholder. It indicates that the Dosing Control Unit (DCU) has detected a fault and sent an error message to the vehicle's main display, but the display's software does not recognize the specific code to translate it into a standard text warning. It means there is an active issue within the emissions/DEF system, but 19999 itself does not point to a specific hardware failure.

• Tier 4a
• Case IH Magnum series (235, 260, 290, 315, 340)
• Case IH STX Steiger series (350, 400, 450, 500, 550, 600)
• Case IH AFX Combines (e.g., 8230, 9230)

1. 1

   Connect the CNH Electronic Service Tool (EST) or the EASY diagnostic tool to the machine's diagnostic port

2. 2

   Ping the Engine Control Unit (ECU) and the Dosing Control Unit (DCU) directly to pull the actual underlying fault code (e.g., P-codes or specific DEF pressure/temperature codes)

3. 3

   Inspect the CAN-bus communication wiring harness between the DCU and the cab display for corrosion or pin damage, which can corrupt the code messages being sent

1. 1

   Depressurize and Disconnect

   Turn off the machine and disconnect the battery. Ensure the DEF system has completed its purge cycle and is depressurized.

2. 2

   Locate the Module

   Locate the DCU/DEF pump assembly (typically mounted on the chassis near the DEF tank or behind the front right wheel inside a protective metal box).

3. 3

   Remove the Unit

   Disconnect the DEF fluid lines (cap them immediately to prevent crystallization/contamination) and unplug the main electrical wiring harnesses. Unbolt the module from its mounting bracket.

4. 4

   Install the New Unit

   Bolt the replacement module into place, reconnect the fluid lines, and plug in the electrical connectors.

5. 5

   Programming

   A new Bosch DCU or DEF Dosing module must be flashed and programmed to the vehicle's ECU using the CNH EST software. It is not a plug-and-play component.

6. 6

   Clear and Test

   Clear the 19999 code and any underlying codes from the system. Run the machine to operating temperature and perform a manual SCR dosing test via the EST to ensure there are no leaks and the system is functioning.