Case IH 19430 – Engine Control Module (ECM) or Dosing Control Unit (DCU) / SCR Controller: DEF/AdBlue injection quantity has exceeded desired value

This condition indicates that the Selective Catalytic Reduction (SCR) system is injecting more Diesel Exhaust Fluid (DEF/AdBlue) into the exhaust stream than the control module is commanding. The system calculates the required DEF based on engine load, exhaust temperature, and upstream NOx levels. If the downstream NOx sensor detects an anomaly, or if the dosing pump's duty cycle/pressure feedback indicates an over-delivery, the system flags an over-injection fault. This is typically caused by a mechanically stuck-open DEF dosing valve (injector), a ruptured diaphragm in the DEF pump, or skewed NOx sensor readings.

• Tier 4b
• Magnum
• Steiger
• Puma
• Maxxum
• Axial-Flow

1. 1

   Visually inspect the DEF dosing valve (injector) mounted on the exhaust pipe for severe white crystallization (urea buildup), which indicates a leak or a stuck-open nozzle.

2. 2

   Perform a System Pressure Test using the Case IH Electronic Service Tool (EST). The system should build and hold 500-900 kPa; a rapid pressure drop when the pump stops indicates a leaking dosing valve.

3. 3

   Perform a Dosing Quantity Override Test using the diagnostic tool to command a specific injection quantity into a graduated cylinder to verify if actual physical output matches commanded output.

4. 4

   Verify that the upstream and downstream NOx sensors are reading accurately, as a faulty sensor can falsely command maximum DEF injection.

1. 1

   Depressurize the System

   Turn off the machine and wait for the DEF system to complete its purge cycle (usually takes 2-5 minutes after key-off). Do not disconnect lines while the system is pressurized.

2. 2

   Remove the Dosing Valve

   Disconnect the electrical connector and the DEF supply line from the dosing valve. Remove the mounting bolts securing the valve to the exhaust decomposition tube.

3. 3

   Clean the Mounting Boss

   Carefully scrape away any crystallized DEF from the exhaust mounting boss. Ensure no debris falls into the exhaust stream.

4. 4

   Install the New Valve

   Install the new DEF dosing valve using a new OEM gasket. Torque the mounting bolts to the manufacturer's specification.

5. 5

   Reconnect and Prime

   Reconnect the DEF line and electrical connector. Turn the key to the ON position to allow the DEF pump to prime the system.

6. 6

   Clear Codes and Test

   Use the diagnostic tool to clear the fault codes. Run a forced stationary regeneration or a DEF dosing test to verify the repair and ensure there are no leaks.