Case IH 19805 – DCU (Dosing Control Unit): UREA (DEF/Reagent) tank temperature sensor raw voltage signal too high

The UREA (DEF/Reagent) tank temperature sensor is sending a raw voltage signal that is too high, registering as a 'Short circuit high' or 'Short to Battery'. Because of this short circuit, the system reads an implausibly high DEF temperature that does not match the temperature reading coming from the DEF pump module.

• Tier 4a
• Steiger & Rowtrac 350, 400, 450, 500, 550, 600
• Magnum 235, 260, 290, 315, 340
• Puma 125, 150, 165, 185, 200, 210, 220, 240
• Maxxum 115, 125, 135, 145, 150
• Optum 270 CVT, 300 CVT
• Windrowers WD1204, WD1504, WD1904, WD2104, WD2304, WD2504

1. 1

   Stop the engine and allow the machine to cool down completely before beginning diagnostics.

2. 2

   Inspect the DEF tank temperature sensor connector (on the DEF tank head unit) for debris, corrosion, or water ingress, which is commonly caused by aggressive pressure washing.

3. 3

   Check the wiring harness leading to the DCU for chafing, bare wires, or a short to the battery.

4. 4

   Inspect machine grounds (earths) and connector pins for any damage or looseness.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the battery to ensure the DCU is powered down.

2. 2

   Clean the Area

   Thoroughly clean the top of the DEF tank around the sensor/header unit to prevent dirt from falling into the tank during service.

3. 3

   Resolve Wiring Issues

   If water or debris was found in the connector during diagnostics, clean the terminals with electrical contact cleaner, dry thoroughly, and apply dielectric grease. If the harness is damaged, repair or splice the affected wiring.

4. 4

   Replace the Sensor

   If the wiring and connectors are in good condition but the short circuit persists, the DEF tank temperature sensor has failed internally and must be replaced. Remove the mounting bolts/retaining ring for the header unit, extract the old unit, and install the new one, ensuring the O-ring/gasket is seated properly.

5. 5

   Clear Codes

   Reconnect the battery. Use a certified Case IH Electronic Service Tool (EST) to clear the DCU error codes, as clearing them without a proper tool or without fixing the root cause will result in the code returning.