Case IH 19174 – SCR (Selective Catalytic Reduction) system / Engine ECU: DEF/AdBlue dosing valve actuator short circuit in high side failure

The system has detected that the electrical circuit controlling the Diesel Exhaust Fluid (DEF) doser injector is shorted to a high voltage source, preventing the valve from operating correctly to reduce NOx emissions.

• Tier 4b
• 240 Series Axial-Flow Combines
• Magnum (180-380)
• Maxxum (115-150)
• Puma (140-240)
• Optum (270-300)
• Vestrum

1. 1

   Inspect the electrical connector at the DEF dosing valve actuator for moisture, corrosion, or bent pins.

2. 2

   Test the wiring harness between the SCR controller/Engine ECU and the DEF dosing valve for a short circuit to a high voltage source (FMI 12 or 15-18). Look for chafed or melted wire insulation.

3. 3

   If the wiring harness is intact and no external short is found, the short circuit is likely internal to the DEF dosing valve actuator itself.

1. 1

   Power Down

   Cycle the controller power or disconnect the battery to clear active power to the circuit and ensure safety.

2. 2

   Repair Wiring

   If a short is found in the harness during diagnostics, repair or replace the affected wiring section.

3. 3

   Replace the Valve

   If the wiring tests good, the DEF dosing valve (doser injector) has failed internally and must be replaced.

4. 4

   Removal

   Disconnect the electrical connector and the DEF fluid lines from the dosing valve on the exhaust stream.

5. 5

   Installation

   Install the new OEM DEF doser injector. Reconnect the fluid lines and electrical harness.

6. 6

   Clear Codes

   Use a diagnostic tool to clear the 19174 fault code and run the engine to verify that the SCR system resumes normal operation without triggering an engine power loss.