Case IH 19550 (DTC 4B8A) - ECU – ECU: DEF/AdBlue system unable to build sufficient pressure for dosing

The system has detected that the DEF (Diesel Exhaust Fluid) supply module (pump) is failing to build or maintain the required pressure to inject fluid into the SCR (Selective Catalytic Reduction) exhaust system.

• MAXXUM T4E
• 240 Series Axial-Flow (7240, 8240, 9240)
• 7130
• 7230
• 8230
• 9230
• Magnum (180-370)
• Steiger (350-600)
• Puma
• Maxxum
• Farmall series
• Patriot series (4430)
• Titan series
• Case CE Skid Steers
• Compact Track Loaders (CTLs)
• Wheel Loaders
• Farmlift Telehandlers

1. 1

   Inspect the DEF supply module filtration system (both the main filter and the pre-filter) for severe clogging or crystallization.

2. 2

   Check all DEF supply and backflow lines for kinks, leaks, or blockages.

3. 3

   Fill a flushing reservoir with one gallon of distilled or de-ionized water. Apply pressure to the reservoir to fill the supply tubing with water, attach the tubing to the inlet connection, and flush the system to clear out crystallized DEF.

4. 4

   Using the electronic diagnostic tool (EASY Engine Diagnostic Tool), run the Urea Dosing System Test (UDST) routine. Monitor the highest and lowest pressures the DEF reaches during the test to verify if the pump is mechanically capable of building pressure.

5. 5

   Inspect the dosing nozzle (injector) in the exhaust stream for heavy crystallization that could be deadheading the pressure.

1. 1

   Relieve Pressure & Clean

   Ensure the machine is off and the DEF system has completed its purge cycle. Clean the area around the DEF supply module to prevent dirt ingress.

2. 2

   Replace Filters

   Remove and replace the DEF supply module main filter and pre-filter (this is the most common cause of pressure buildup failure).

3. 3

   Flush the Lines

   Perform the distilled/de-ionized water flushing procedure outlined in the diagnostic steps to clear out the supply lines and dosing nozzle.

4. 4

   Clean/Replace Dosing Nozzle

   If the nozzle is heavily crystallized and cannot be cleared by flushing, remove it from the exhaust pipe, clean it with warm distilled water, or replace it.

5. 5

   Replace Supply Module

   If the filters are new, the lines are clear, and the UDST still shows the system cannot build pressure, the internal pump of the DEF Supply Module has failed. Remove the DEF lines and electrical connectors, unbolt the module from its bracket, and install a new DEF Supply Module.

6. 6

   Clear Codes & Retest

   Clear the 19550 / 4B8A fault codes using the diagnostic tool and run a final UDST to verify the system builds and maintains proper dosing pressure.