Case IH 19078 – Engine Control Module (ECM) or Urea Supply Computer / DEF Dosing Control Unit: System not emptied at the end of the previous driving cycle

A Diesel Exhaust Fluid (DEF) / Urea system fault where the shutdown purge cycle fails to complete successfully. When a Tier 4B machine is shut down, the emissions system must run a purge cycle to empty the DEF fluid from the lines and dosing injector back into the tank to prevent freezing and crystallization.

• Tier 4b
• T7 series
• Magnum
• Steiger
• Farmall

1. 1

   Verify operator habits: ensure the main battery disconnect switch is not being turned off immediately after the ignition key is turned off, as the DEF system requires continuous battery power for several minutes to purge.

2. 2

   Check for related electrical fault codes (19082, 19083, and 19084) that indicate a circuit failure preventing the purge.

3. 3

   Inspect the DEF lines between the tank, the supply pump, and the dosing valve for physical blockages, kinks, or frozen fluid.

4. 4

   Connect the Case IH Electronic Service Tool (EST) to monitor the DEF system parameters and manually command a purge cycle to see if the pump and reversing valve actuate.

1. 1

   Retrieve fault codes

   Connect the Case IH Electronic Service Tool (EST) to the machine's diagnostic port to retrieve all active and stored fault codes.

2. 2

   Test and repair wiring harness

   If codes 19082, 19083, or 19084 are present alongside 19078, use a multimeter to test the wiring harness between the Urea Supply Computer and the DEF reversing valve for continuity, shorts to ground, or shorts to power. Repair any damaged wiring.

3. 3

   Inspect and clean DEF components

   Inspect the DEF dosing valve actuator and the DEF supply pump for mechanical failures or heavy crystallization. Clean any crystallized urea with warm water.

4. 4

   Replace faulty components

   If the wiring is intact but the system still fails to empty the lines during an EST-commanded purge test, the DEF reversing valve or the DEF supply pump assembly has failed internally and must be replaced.

5. 5

   Verify repair

   After replacing the faulty component, use the EST to clear the fault codes. Run the engine, perform a normal key-off shutdown, and wait for the DEF pump to complete its audible purge cycle to verify the repair.