Case IH 17746 (F-519055-31) - ECU – Engine Control Unit (ECU): Urea injection interrupted for a long period of time due to urea under pressure faults

The Selective Catalytic Reduction (SCR) system is failing to build or maintain the required Diesel Exhaust Fluid (DEF/AdBlue) pressure to inject fluid into the exhaust stream, causing the system to halt dosing to protect the components.

• VESTRUM CVX
• Farmall 40
• Farmall 45
• Farmall 50
• Farmall 90C
• Farmall 95A
• Farmall 115U
• Farmall 120C
• Farmall 130A
• Maxxum 115
• Maxxum 125
• Maxxum 135
• Maxxum 145
• Maxxum 150
• Puma 140
• Puma 150
• Puma 165
• Puma 185
• Puma 200
• Puma 220
• Puma 240
• Magnum 180
• Magnum 200
• Magnum 220
• Magnum 240
• Magnum 250
• Magnum 280
• Magnum 310
• Magnum 340
• Magnum 380
• Steiger Series
• Combine 9230

1. 1

   Reboot the system by turning the tractor completely off and back on to rule out a transient software glitch.

2. 2

   Check the WEMA Unit (DEF Tank Assembly) suction tube and O-ring for cracks that could cause the pump to suck air (loss of prime cause).

3. 3

   Check the DEF Tank Heater Control Valve (Coolant Control Valve) to ensure it is not stuck open, which overheats the DEF tank and damages the sensor.

4. 4

   Inspect DEF lines and dosing valve for leaks, crystallization, blockages, or a stuck closed valve.

5. 5

   Run laptop diagnostics (UDST tests) to monitor exact pressure output of the supply module and verify pressure sensor readings.

1. 1

   Inspect and Pressurize the Suction Tube

   Remove the WEMA unit from the DEF tank. Lightly pressurize the suction tube and apply slight physical flex to check for hairline cracks at the top O-ring seal. If it leaks air, replace the WEMA unit or repair the O-ring seal.

2. 2

   Test the DEF Supply Pump

   If the suction line is intact but the system still cannot build pressure during the laptop dosing test, the DEF Supply Pump (Dosing Module) has likely failed internally and must be replaced.

3. 3

   Replace the DEF Filter

   Whenever opening the DEF system or replacing the pump, replace the main DEF filter to ensure no crystallized DEF or debris damages the new components.

4. 4

   Check/Replace the Dosing Valve

   If the pump builds pressure but fluid is not injecting (or if the valve is leaking pressure into the exhaust), remove the DEF doser injector from the exhaust pipe. Clean any crystallized DEF. If the mechanical system is not responding, replace the doser injector.

5. 5

   Clear Codes and Retest

   Use the diagnostic tool to clear fault code 17746. Run a stationary forced dosing test to ensure the system builds and holds the correct urea pressure without air intrusion.