Case IH 19335 – ECU or DCU: Pressure build-up error / DEF/ADBLUE® system unable to build sufficient pressure for dosing

To prevent freezing damage to the dosing valve, the DEF (Diesel Exhaust Fluid) system is evacuated every time the engine is shut down. Upon the next engine start, the system must refill and pressurize. The pressure build-up happens in two phases: first to 1.0 bar (14.5 psi), and then up to 3.5 bar (50.8 psi) to enter the normal 'metering control state.' If the system fails to reach this pressure within a specific timeframe or number of cycles, it enters a stand-by state, triggers a derate, and logs fault code 19335.

• Tier 4b
• Steiger
• Magnum (235-340)
• Puma
• Farmall
• Maxxum
• Axial-Flow (5140, 6150, 7150, 9230)
• Patriot
• TV380
• Wheel Loaders (721F, 821F, 921F, 1021G, 1121G)

1. 1

   Check for a faulty or empty DEF/AdBlue fluid level

2. 2

   Verify that the DEF suction and back-flow lines are not crossed at the DEF supply module (pump) or the tank

3. 3

   Inspect the DEF back-flow line for blockages and the pressure line for heavy fluid leakage

4. 4

   Check the DEF tank vent to ensure it is not blocked, which can create a vacuum and prevent fluid draw

5. 5

   Inspect the DEF tank suction-side sending unit for air leaks (look for a hairline crack in the suction tube at the top of the tank unit)

6. 6

   Check the DEF tank suction-side pre-filter and the main DEF supply module filter for severe clogging

1. 1

   Drain and Inspect

   Drain the DEF tank to check for fluid contamination or crystallization. Refill with fresh, high-quality DEF.

2. 2

   Inspect Plumbing

   Visually inspect all DEF lines (suction, pressure, and backflow) for kinks, leaks, or blockages. Ensure they are routed to the correct ports.

3. 3

   Replace Filters

   Replace the main DEF filter cartridge located in the supply module, as well as the suction pre-filter in the tank sending unit.

4. 4

   Test for Air Intrusion

   Pressurize the suction tube assembly in the DEF tank to check for hairline cracks. If the tube is cracked and drawing air, replace the tank sending unit assembly.

5. 5

   Replace the DEF Pump

   If all lines, filters, and tank units are intact, the fault is likely caused by a failed pump membrane or a failed internal pressure sensor within the DEF supply module (Pump A-021). Replace the DEF pump assembly.

6. 6

   Reprogram and Clear

   Note that a new DEF supply module may need to be programmed to the vehicle's ECU/DCU after installation. Clear the fault codes and run an SCR system test to verify the system successfully builds and holds 3.5 bar (50.8 psi) of pressure.