Case IH 19793 – DCU15: Group error path UREA Tank empty / Reagent - fluid level in tank - Too low

The Selective Catalytic Reduction (SCR) system has detected that the Diesel Exhaust Fluid (DEF) / AdBlue tank is empty, or the DEF level sensor is reporting a critically low fluid level to the system.

• Tier 4b
• Case IH Magnum 235 - 340 (Series 4)
• Case IH STX Steiger (350 to 600 HP)
• Case IH Farmall series
• Case 721F
• Case 821F
• Case 921F

1. 1

   Manual Level Check: Manually check the actual DEF fluid level in the tank and compare it to the level reported by the sensor on the cab monitor. If the tank is empty, the sensor is reading correctly.

2. 2

   Fluid Quality Inspection: Inspect the DEF fluid quality. Poor-quality, degraded, or contaminated fluid can cause chemical reactions, scale buildup (white deposits), and crystallization that mimics a sensor failure. Test for proper urea concentration (32.5% urea to 67.5% distilled water) using a refractometer.

3. 3

   Wiring and Connector Check: Examine the DEF level sensor wiring harness and connectors. Look for signs of corrosion, pin damage, or loose connections between the sensor and the ECU.

4. 4

   Visual Inspection: Look for physical cracks, wear, or heavy crystallization around the DEF head unit flange on top of the tank.

1. 1

   Refill the Tank

   If the tank is physically empty, refill the DEF tank with high-quality, ISO 22241 compliant DEF/AdBlue. Cycle the key to see if the fault becomes inactive.

2. 2

   Address Fluid Contamination

   If the fluid concentration is incorrect or contaminated, drain the tank, flush it, and replace the DEF/AdBlue.

3. 3

   Inspect the Harness

   If the tank is full but the code persists, disconnect the DEF level sensor connector. Ensure the pins are in the correct position, the fit is tight, and there is no corrosion. Repair or replace the wiring harness if continuity is broken.

4. 4

   Replace the DEF Head Unit

   If the wiring is intact and the fluid is at the correct concentration, the DEF Head Unit / Level Sensor has likely failed internally. Remove the faulty DEF Head Unit from the top flange of the DEF tank and install the replacement unit.

5. 5

   Clear Codes

   Reconnect the wiring harness. Use an Electronic Service Tool (EST) to clear the fault code, or cycle the ignition to verify the fault code is no longer active.

6. 6

   Verify Operation

   Verify the SCR system is operating properly and return the machine to operation.