Case IH 19791 – Vehicle Control Module (VCM) or Engine Control Module (ECM) / Dosing Control Unit (DCU): Level 3 warning is active due to Low DEF/AdBlue Level

The Selective Catalytic Reduction (SCR) system has detected that the Diesel Exhaust Fluid (DEF) tank is critically low or empty, triggering a Level 3 Inducement that limits the machine's engine power and speed until the DEF level is restored.

• Tier 4b
• N-Series Loader Backhoes
• Magnum
• Steiger
• Puma
• Optum
• Farmall
• T7 Series
• TR340
• 7230
• 8230

1. 1

   Verify physical fluid level: Check the actual physical level of DEF in the tank. If it is genuinely empty, simply refilling the tank with high-quality DEF and allowing the system to reset may clear the code.

2. 2

   Inspect for sensor failure: If the tank is full but the gauge reads empty, the DEF level sensor (integrated into the DEF Header Unit) has likely failed, become stuck, or crystallized.

3. 3

   Check for contamination: Inspect the DEF fluid for contamination, such as accidental cross-contamination with diesel fuel, which causes chemical reactions that destroy plastics and sensors.

4. 4

   Inspect wiring: Check the wiring harness and electrical connector at the DEF header for corrosion, moisture intrusion, or broken wires that could cause a false empty reading.

1. 1

   Prep the Machine

   Turn off the engine, remove the key, and disconnect the battery.

2. 2

   Clean the Area

   Thoroughly clean the top of the DEF tank and the area around the DEF header unit. It is critical that no dirt, debris, or crystallization falls into the tank during removal.

3. 3

   Disconnect Lines

   Carefully disconnect the electrical harness connector and the DEF supply/return lines from the top of the header unit.

4. 4

   Remove the Header

   Remove the mounting bolts or retaining ring securing the DEF header to the tank.

5. 5

   Extract the Sensor

   Carefully pull the DEF header unit (which houses the level float/ultrasonic sensor, temperature sensor, and quality sensor) straight up and out of the tank.

6. 6

   Flush Tank (If Necessary)

   If contamination (like diesel fuel) or heavy crystallization is found, the entire DEF tank must be drained and flushed with distilled water before installing the new sensor.

7. 7

   Install New Unit

   Insert the new DEF header unit into the tank, ensuring the new mounting seal/O-ring is properly seated to prevent leaks.

8. 8

   Reassemble

   Secure the mounting hardware, then reconnect the DEF fluid lines and the electrical connector.

9. 9

   Refill and Reset

   Refill the tank with fresh, uncontaminated DEF. Reconnect the battery. You will likely need to use the Case IH Electronic Service Tool (EST) laptop to clear the hard inducement fault codes and reset the SCR system logic.