Case IH 19873 – Engine Control Unit (ECU) / Heater Control Unit (HCU) / Dosing Control Unit (DCU): PRC high for Current at DEF/AdBlue Supply module Heater (via HCU)

The Physical Range Check (PRC) has detected an abnormally high electrical current draw on the DEF Supply Module's internal heater circuit, indicating a short to ground in the wiring harness or an internal short circuit within the heater element.

• Tier 4b
• Tier 4 Final
• Magnum
• Maxxum
• Puma
• Steiger
• Optum
• Vestrum
• Farmall
• Axial-Flow 5130
• Axial-Flow 6130
• Axial-Flow 7130
• Axial-Flow 7230
• Axial-Flow 8230
• Axial-Flow 9230
• Patriot 3030
• Patriot 3530
• Patriot 4030
• Patriot 4530
• Titan 3030
• Titan 3530
• Titan 4030
• Titan 4530
• 580SN Backhoes
• 521F Wheel Loaders
• 1150M Dozers
• Farmlift Telehandlers

1. 1

   Visual Wiring Inspection: Trace the wiring harness from the Heater Control Unit (HCU) to the DEF Supply Module. Look for chafed insulation, pinched wires against the frame, or melted casing that could cause a short to ground.

2. 2

   Connector Check: Disconnect the DEF Supply Module and the HCU. Inspect the pins for corrosion, bent terminals, or water intrusion, which can bridge connections and cause high current readings.

3. 3

   Resistance Test (Ohm out the Heater): With the DEF Supply Module unplugged, use a multimeter to measure the resistance across the heater circuit pins on the module side. If the resistance is near zero (continuity to ground), the internal heater element is shorted, and the module must be replaced.

4. 4

   Harness Short Test: Check for continuity between the heater power supply wire in the harness and the chassis ground. If there is continuity while unplugged from the module, the wiring harness is shorted and needs repair.

1. 1

   Preparation

   Turn off the ignition, remove the key, and disconnect the battery to prevent electrical spikes. Wait at least 10 minutes for the DEF system to purge and depressurize.

2. 2

   Locate the Module

   Locate the DEF Supply Module (usually mounted on a bracket directly adjacent to or on top of the DEF tank).

3. 3

   Disconnect Lines

   Carefully disconnect the DEF suction, pressure, and backflow lines. Note: DEF is corrosive; clean up any spills immediately with warm water.

4. 4

   Disconnect Electrical

   Unplug the main electrical harness connector from the module.

5. 5

   Removal

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

6. 6

   Installation

   Mount the new DEF Supply Module and torque the bolts to OEM spec.

7. 7

   Reconnection

   Reconnect the DEF fluid lines (ensure they click securely into place) and plug in the electrical connector.

8. 8

   Filter Replacement

   It is highly recommended to replace the DEF Supply Module filter during this service if the new unit does not come with one pre-installed.

9. 9

   Clear Codes & Prime

   Reconnect the battery. Turn the ignition on and use a diagnostic scan tool (like CNH EST) to clear fault code 19873. Run a DEF system prime/leak test via the scan tool to ensure the pump builds pressure and there are no leaks.