Case IH 19109 – DCU (Dosing Control Unit): UREA Temperature sensor in Tank (electrical) - signal high - short circuit high

The voltage signal from the Diesel Exhaust Fluid (DEF/Urea) tank temperature sensor has exceeded the maximum allowable limit. The system interprets this as an electrical fault—specifically, a short circuit to a high-voltage source (like battery positive) or an open circuit that defaults to a high voltage reading.

• Tier 4a
• Magnum Series 235, 260, 290, 315, 340 (Series 4)
• Steiger & Rowtrac Series 350, 400, 450, 500, 550, 600
• Puma Series 150, 165, 185, 200, 220, 240
• Farmall Series 90C, 110U

1. 1

   Inspect the wiring harness between the DEF tank sending unit and the DCU. Look for chafed wires, melted insulation, or pinched lines that could cause a short to battery voltage.

2. 2

   Disconnect the DEF header connector. Check the pins for white crystalline buildup, corrosion, or moisture.

3. 3

   Hook up a diagnostic laptop (like CNH EST or Cummins INSITE) and read the live DEF tank temperature. Compare it to the ambient temperature. If it reads an impossibly high value (or defaults to a maximum extreme), the circuit is compromised.

4. 4

   Probe the temperature sensor pins on the DEF header itself with a multimeter. If the sensor reads an open circuit (infinite resistance) or a dead short, the internal sensor has failed.

1. 1

   Preparation

   Turn off the machine, remove the key, and disconnect the battery to prevent further electrical shorts.

2. 2

   Clean the Area

   Locate the DEF tank. Thoroughly clean the top of the tank and the area around the DEF header to prevent dirt or debris from falling into the DEF fluid during removal.

3. 3

   Disconnect Lines

   Carefully disconnect the electrical connector and the DEF fluid lines (suction, return, and coolant heater lines) from the DEF header. Note: Mark the coolant heater lines; reversing them can cause the DEF tank to continuously boil.

4. 4

   Remove the Header

   Unscrew the mounting ring or remove the retaining bolts securing the DEF header to the tank. Carefully pull the long sending unit assembly straight up and out of the tank.

5. 5

   Install the New Unit

   Insert the new DEF Head Unit into the tank, ensuring the new rubber gasket/seal is seated properly to prevent leaks. Tighten the mounting ring/bolts to OEM torque specs.

6. 6

   Reconnect

   Reattach the DEF fluid lines, coolant lines, and the electrical connector.

7. 7

   Clear Codes & Heal

   Reconnect the battery. Connect a dealer diagnostic laptop to clear the inactive P205D/19109 code and run a forced SCR system 'healing procedure' to restore full engine power.