Case IH 19794 (DTC F79F) - ECU – Engine Control Unit (ECU) or Aftertreatment / Dosing Control Unit (DCU): SCR Inducement: Level 1 (Torque reduction), triggered by DEF/AdBlue Consumption fault.

The system has detected that the Diesel Exhaust Fluid (DEF) consumption rate is lower than expected or incorrect based on the engine's current operating load and emissions output, triggering a Level 1 Inducement (a forced 25% engine torque reduction).

• MAXXUM T4E
• Magnum series (235, 260, 290, 315, 340, 370)
• Steiger series (450, 620)
• Puma series (e.g., 185)
• T7 series
• Titan Floater Sprayers (3040, 3540, 4040, 4440, 4540)
• Case CE 850M crawler dozer
• Case CE 1650M crawler dozer

1. 1

   Inspect the DEF tank for contaminated, degraded, or expired fluid. DEF crystallizes when exposed to air or degrades in high heat, which is a primary cause of consumption faults.

2. 2

   Check the DEF injector nozzle and DEF supply lines for white, crusty urea crystallization that physically blocks fluid flow.

3. 3

   Using an Electronic Service Tool (EST), perform a Urea Dosing System Test (UDST). The system pressure should typically hold between 4900 to 6200 millibar (71.1 to 89.9 psi). If it cannot build or maintain pressure, the pump or filter is failing.

4. 4

   Verify that the upstream and downstream NOx sensors are reading correctly. If a NOx sensor sends inaccurate data to the ECU, the system will dose the wrong amount of DEF, triggering a consumption fault.

1. 1

   Drain and flush DEF tank

   If the DEF is contaminated, cloudy, or smells incorrect, drain the DEF tank completely and flush the system.

2. 2

   Replace DEF filter

   Remove the old DEF supply filter (usually located near the supply pump) and install a new one to ensure unrestricted flow.

3. 3

   Clean or replace DEF injector

   Remove the DEF doser injector from the exhaust stream. If it is heavily crystallized, carefully clean the nozzle. If it is mechanically failed or permanently clogged, replace the injector.

4. 4

   Replace DEF supply pump

   If the system failed the UDST pressure test in the diagnostic phase (unable to build or maintain 4900 to 6200 millibar), replace the DEF supply pump module.

5. 5

   Refill and prime

   Refill the tank with fresh, ISO-compliant DEF.

6. 6

   Clear codes and test

   Connect the diagnostic service tool, clear the F79F / 19794 fault codes, and run a forced SCR dosing test or stationary regeneration to verify that DEF is flowing at the correct rate and the Level 1 derate is lifted.