Case IH 19336 – DCU (Dosing Control Unit): System frozen and not free in time | Defreezing Mode and Detection Errors (pressure build-up in detection mode failed) | P20C5 Pump module - Internal heating - open circuit.

The internal electrical heater inside the DEF (Diesel Exhaust Fluid) pump module has suffered an open circuit. Because the heater cannot operate, the system is unable to thaw frozen DEF fluid within the programmed time limit during cold weather. Consequently, the pump is blocked by frozen fluid and fails to build up the required pressure during the system's defreezing and detection mode.

• Tier 4a
• Magnum series (180 through 405, Series 4)
• Steiger series (350 through 620)
• Puma series (140 through 240)
• Maxxum series (115 through 150)
• Optum
• Farmall (90C, 95A, 130A)
• Axial-Flow series (5150, 6140, 7140, 7240, 8240, 9240, etc.)
• Patriot series
• Trident series
• Titan series

1. 1

   Inspect the wiring harness between the DCU and the DEF pump module for any signs of chafing, breaks, or rodent damage that could cause an open circuit.

2. 2

   Disconnect the electrical connector at the DEF pump module. Check for corrosion, moisture, or pushed-out pins.

3. 3

   Using a multimeter, test the resistance of the internal heater circuit directly at the DEF pump module's pins. If the multimeter reads an open circuit (infinite resistance/OL), the internal heater has failed, confirming the pump module itself is the culprit.

4. 4

   Verify that the power supply and fuses for the DEF heating system (UB1/UB2 circuits) are intact and delivering voltage to the pump.

1. 1

   Disconnect battery

   Turn off the ignition and disconnect the machine's battery to prevent electrical shorts.

2. 2

   Locate DEF pump module

   Locate the DEF pump module (usually mounted near the DEF tank).

3. 3

   Clean area

   Thoroughly clean the outside of the pump and surrounding area to prevent dirt from contaminating the sensitive SCR system.

4. 4

   Disconnect electrical harness

   Disconnect the electrical harness connectors from the DEF pump.

5. 5

   Disconnect fluid lines

   Carefully disconnect the DEF suction, pressure, and backflow lines. Cap or plug the lines immediately to prevent fluid loss and contamination.

6. 6

   Remove faulty module

   Remove the mounting bolts and remove the faulty DEF pump module.

7. 7

   Install new module

   Install the new DEF pump module and secure the mounting hardware.

8. 8

   Reconnect fluid lines

   Reconnect the DEF fluid lines, ensuring the quick-connect fittings click securely into place.

9. 9

   Reconnect electricals

   Reconnect the electrical harness and the battery.

10. 10

    Clear fault codes

    Use a Case IH Electronic Service Tool (EST) to clear the fault codes.

11. 11

    Run system test

    Run a dynamic DEF system leak and dosing test via the EST to verify that the pump builds pressure and the heater circuit is recognized.