Case IH 19140 (DTC 4BCA) - ECU – DCU (Dosing Control Unit): DEF/AdBlue concentration is out of range.

The system has detected that the Diesel Exhaust Fluid (DEF) in the tank does not meet the required 32.5% urea concentration. This is measured by the DEF quality sensor. The fluid may be diluted with water, degraded from age/heat, or the sensor itself may be failing due to internal corrosion or rationality issues.

• MAXXUM T4E
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Magnum
• Puma
• Optum
• Maxxum (115 onwards)

1. 1

   Test the DEF concentration in the tank using a DEF refractometer. It should read exactly 32.5% urea. If it is diluted or degraded, the fluid is the problem, not the sensor.

2. 2

   Check for signs of diesel fuel or water in the DEF tank. (Note: If diesel fuel is detected, the system will usually throw a companion code, 19141 / DTC 4CCA).

3. 3

   Inspect the DEF quality sensor (located on the top of the DEF tank header unit). Early designs were prone to ammonia gas leaking into the sensor housing, which corrodes the internal circuit boards.

4. 4

   Inspect the DEF quality sensor wiring harness and connectors for corrosion, moisture, or physical damage.

1. 1

   Drain and Flush

   If the DEF is degraded, diluted, or contaminated, completely drain the DEF tank. Flush the tank to remove any crystallized urea or contaminants.

2. 2

   Refill

   Refill the tank with fresh, high-quality DEF from a sealed container.

3. 3

   Test

   Clear the fault codes using a diagnostic tool and run the machine to see if the code returns.

4. 4

   Sensor Replacement

   If the code persists after fresh fluid is introduced (or if the sensor is visibly corroded/failed), the DEF quality sensor/header unit must be replaced.

5. 5

   Installation

   Disconnect the battery, unplug the electrical connector and fluid lines from the top of the DEF header, unbolt the header assembly from the tank, and carefully extract it. Install the new header unit, reconnect the lines and harness, and clear the codes. (Note: On some newer software revisions, manufacturers have released updates that bypass the quality sensor requirement and rely solely on the NOx sensors, but this requires a dealer software flash).