Case IH 19429 – Engine Control Module (ECM): DEF/AdBlue injection quantity has exceeded desired value

The system detects that the volume of Diesel Exhaust Fluid (DEF) being dosed into the Selective Catalytic Reduction (SCR) system is higher than the amount commanded by the engine's mapping. This is typically caused by a mechanically stuck-open DEF dosing injector, a ruptured DEF line, or a dosing pump/supply module that is over-pressurizing the fluid.

• Tier 4b
• Case IH Steiger
• Case IH Magnum
• Case IH Puma
• Case IH Optum
• Case IH Patriot Sprayers (e.g., 3340)
• Case IH Axial-Flow Combines (e.g., 8240)
• Case Crawler Dozers
• Case Excavators

1. 1

   Visual Leak Inspection: Inspect the DEF dosing lines and connections between the DEF supply module (pump) and the DEF injector for external leaks or ruptures.

2. 2

   Injector Inspection: Remove the DEF injector from the exhaust pipe and inspect the nozzle. Look for severe DEF crystallization, physical damage, or signs that the pintle is mechanically stuck open.

3. 3

   Electrical Testing: Check the wiring harness and connector going to the DEF injector. A short to power or ground in the harness could be falsely commanding the injector to stay open.

4. 4

   Pressure Test: Use the Electronic Service Tool (EST) to monitor the DEF supply module pressure. Ensure the pump is not over-pressurizing the system.

5. 5

   Fluid Quality: Verify the DEF fluid quality and concentration using a refractometer to rule out contaminated fluid causing internal injector binding.

1. 1

   Purge Cycle

   Turn off the machine's ignition. Crucial: Wait at least 2 to 5 minutes for the DEF system to complete its automatic purge cycle. You will hear the DEF pump running as it pulls fluid back into the tank to prevent freezing.

2. 2

   Disconnect Power

   Once the purge is complete, disconnect the negative battery cable.

3. 3

   Disconnect Injector

   Locate the DEF dosing injector on the exhaust/SCR mixing tube. Disconnect its electrical connector.

4. 4

   Remove Lines

   Carefully disconnect the DEF supply line and the engine coolant lines (if equipped with a heated injector) from the dosing module. Cap the lines immediately to prevent contamination.

5. 5

   Remove Injector

   Remove the V-band clamp or mounting screws securing the DEF injector to the exhaust boss.

6. 6

   Clean the Boss

   Remove the old injector and thoroughly clean the mounting boss on the exhaust pipe. Ensure no carbon or crystallized DEF debris falls into the exhaust stream.

7. 7

   Install New Injector

   Install the new DEF dosing injector using a new mounting gasket/clamp. Torque the clamp/screws to OEM specifications.

8. 8

   Reconnect

   Reconnect the DEF supply line, coolant lines, and the electrical connector.

9. 9

   Restore Power

   Reconnect the negative battery cable.

10. 10

    Clear and Test

    Connect the CNH Electronic Service Tool (EST). Clear fault code 19429. Run a manual DEF dosing system test (or SCR system test) via the software to verify that the injection quantity now matches the desired value and that there are no leaks.