Case IH 19079 – Engine Control Unit (ECU) or Dosing Control Unit (DCU): DEF/AdBlue over pressure failure

The Selective Catalytic Reduction (SCR) system has detected that the fluid pressure within the Diesel Exhaust Fluid (DEF) supply lines has exceeded the maximum allowable threshold. This can be caused by a physical blockage in the system, a failed pressure sensor, or a malfunctioning DEF supply pump that is failing to regulate pressure.

• Tier 4b
• 240 Series Axial-Flow (7240, 8240, 9240)
• 130 and 230 series (5130, 6130, 7130, 7230)
• Steiger (350 to 600)
• Magnum (180 to 370)
• Puma (130 to 240)
• Maxxum (110 to 140)
• Farmall series
• Patriot Sprayers (4430)
• Titan Floaters (3030, 4030)
• Farmlift Telehandlers

1. 1

   Check for cascading electrical faults (codes 19047 or 19111) to rule out wiring harness or sensor failures

2. 2

   Inspect the DEF dosing valve (injector) for heavy crystallization or blockages causing fluid backup

3. 3

   Inspect DEF supply and return lines between the pump and doser for kinks, crushing, or freezing

4. 4

   Check the return flow line to the DEF tank to ensure it is clear, allowing the pump to bleed off excess pressure

1. 1

   Power Down

   Turn off the machine ignition. Crucial: Wait at least 2 to 5 minutes before disconnecting the battery to allow the DEF system to complete its automatic purge cycle. Interrupting this cycle can damage the system.

2. 2

   Clean the Doser

   If crystallization was found during diagnostics, clean the dosing valve and the mounting port using warm distilled water (do not use harsh chemicals or brake cleaner).

3. 3

   Remove the DEF Supply Module

   Disconnect the electrical harness connectors from the DEF pump. Disconnect the DEF suction, pressure, and return lines.

4. 4

   Dismount

   Unbolt the DEF supply module from its mounting bracket and remove it from the machine.

5. 5

   Install New Module

   Mount the replacement DEF Supply Module. Reconnect the fluid lines (ensure they click securely into place to prevent leaks) and plug in the electrical harness.

6. 6

   Replace Filters

   Always install a new DEF supply module main filter and inline filter when replacing the pump to prevent old debris from ruining the new unit.

7. 7

   Clear Codes and Test

   Connect a diagnostic tool (such as CNH EST) to clear the 19079 fault code. Start the engine and allow it to reach operating temperature so the SCR system begins dosing. Verify that the pressure normalizes and the engine derate is lifted.