Case IH 19046 – DCU (Dosing Control Unit): UREA pressure sensor in box (electrical) | supply voltage error | P204A Reagent - pressure sensor - open circuit

This code indicates an electrical failure—specifically an open circuit or a supply voltage error—in the Diesel Exhaust Fluid (DEF/Urea) pressure sensor circuit. The sensor is located inside the DEF pump module (supply module). When the controller detects that the sensor's signal is missing or the voltage is out of range, it logs this code and will likely derate the engine to comply with emissions standards.

• Tier 4a
• Magnum (235-340 Series 4, 180-250)
• Steiger (350-600 HP)
• Puma (150-200)
• Maxxum (115-145)
• Optum
• Farmall
• Combine 5130
• Combine 6130
• Combine 7130
• Combine 7230
• Combine 8230
• Combine 9230
• Combine 40/50/60 series
• Patriot 2250
• Patriot 3240
• Patriot 3340
• Trident 5550

1. 1

   Inspect the main electrical harness connector plugging into the DEF pump module for corrosion, bent pins, or moisture intrusion

2. 2

   Check the wiring harness running between the DCU and the DEF pump module for chafing, breaks, or rodent damage

3. 3

   Using a multimeter, verify that the DCU is sending the correct 5V reference voltage and ground to the DEF pressure sensor pins on the harness side

4. 4

   If the wiring harness has continuity and the 5V supply/ground are present, the internal pressure sensor inside the DEF pump module has failed

1. 1

   Turn off the machine, remove the key, and disconnect the battery

   This prevents electrical shorts and depressurizes the system.

2. 2

   Locate the DEF pump module assembly

   Usually mounted near the DEF tank.

3. 3

   Thoroughly clean the area around the pump

   This prevents dirt from entering the DEF lines, as the SCR system is highly sensitive to contamination.

4. 4

   Disconnect the electrical harness from the module

5. 5

   Disconnect the DEF suction, pressure, and backflow lines

   Have a catch pan ready for minor fluid spills.

6. 6

   Unbolt the DEF pump module from its mounting bracket and remove it

7. 7

   Install the new DEF pump module

   Torque the mounting bolts to OEM spec.

8. 8

   Reconnect the DEF fluid lines and electrical harness

   Ensure the fluid lines click securely into place.

9. 9

   Reconnect the battery

10. 10

    Connect a diagnostic laptop with CNH Electronic Service Tool (EST)

    The new module will likely need to be programmed/calibrated to the vehicle's DCU.

11. 11

    Clear the 19046 / P204A fault codes and run a DEF system leak test or dosing test

    Perform this via the diagnostic software to verify the repair.