Case IH 19874 – HCU: PRC low for Current at DEF/AdBlue Supply module Heater (via HCU)

The current drawn by the DEF (Diesel Exhaust Fluid) Supply Module Heater is lower than the expected physical range. This typically points to an open circuit, high resistance in the wiring, or a burned-out heater element inside the DEF supply module.

• Tier 4b
• Magnum (180-370)
• Maxxum (110-140)
• Puma (130-215)
• Steiger (350-600)
• Farmall (95A, 100C, 110C)
• 5130
• 6130
• 7130
• 7230
• 8230
• 9230
• Patriot 4430
• Titan 3030
• Titan 3530
• Titan 4030
• Titan 4530
• Farmlift series
• N-Series Tractor Loader Backhoes (TLBs)
• 521F
• 821F
• 921F
• 1150M

1. 1

   Turn OFF the ignition switch and wait until communication with the diagnostic scan tool is completely discontinued to ensure the system has powered down

2. 2

   Inspect the control circuit and wiring harness between the HCU and the DEF Supply Module for chafed wires, disconnected plugs, or corrosion that could cause an open circuit (low current)

3. 3

   Verify the DEF Supply Module Heater relay is functioning and supplying proper voltage (normally open standard relay, 12V or 24V depending on the machine)

4. 4

   Check for accompanying codes that might indicate a broader power issue, such as 19879 (Heater control unit reports missing voltage at Terminal 30) or 19872 (Power stage error in HCU for DEF/AdBlue Supply Module Heater)

5. 5

   Test the resistance of the heater element directly at the DEF Supply Module pins. If the internal heater is open (infinite resistance), the module must be replaced

1. 1

   Power down system

   Park the machine on a level surface, turn off the engine, and allow the DEF system to complete its purge cycle and power down completely.

2. 2

   Locate module

   Locate the DEF Supply Module (typically mounted near or on the DEF tank).

3. 3

   Clean area

   Thoroughly clean the area around the module to prevent dirt from entering the DEF lines.

4. 4

   Disconnect harness

   Disconnect the electrical harness connector from the DEF Supply Module.

5. 5

   Disconnect lines

   Disconnect the DEF suction, pressure, and backflow lines. (Note: Be prepared for minor fluid spillage; cap the lines immediately to prevent contamination).

6. 6

   Remove module

   Remove the bolts securing the DEF Supply Module to its mounting bracket and remove the unit.

7. 7

   Install new module

   Install the new DEF Supply Module onto the bracket and secure the mounting hardware.

8. 8

   Reconnect lines and harness

   Reconnect the DEF fluid lines and the electrical harness.

9. 9

   Clear codes

   Turn the ignition switch ON (without starting the engine) and use a diagnostic scan tool to clear the 19874 fault code (and any related codes like P20C9).

10. 10

    Test operation

    Start the engine, run it at idle speed, and inspect all connections for DEF leaks.