Case IH 19048 – DCU (Dosing Control Unit): UREA pressure sensor in box (electrical) | signal low | P204C Reagent - pressure sensor - short circuit low

The signal voltage from the Diesel Exhaust Fluid (DEF/Urea) pressure sensor has dropped below the minimum acceptable threshold. The system has detected a short circuit to a low voltage source (ground) within the sensor circuit located inside the DEF pump module (the "box").

• Tier 4a
• Tier 4b
• Case IH Magnum Series
• Case IH Steiger Series
• Case IH Puma Series

1. 1

   Inspect the wiring harness connecting the DCU to the DEF pump module for chafed insulation, pinched wires, or areas rubbing against the chassis causing a short to ground.

2. 2

   Disconnect the electrical harness at the DEF pump module and check for water intrusion, DEF crystallization, or bent/corroded pins.

3. 3

   With the sensor disconnected, turn the key ON and check if the active fault code changes from 19048 to 19046 / P204A (Open Circuit). If it changes, the short is internal to the DEF pump module. If it remains 19048, the short is in the wiring harness.

4. 4

   If no short circuit is found in the wiring and the sensor tests fine, test the DCU itself with a known-good controller as it may have an internal failure.

1. 1

   Power Down

   Turn off the tractor, remove the key, and turn off the battery disconnect switch to prevent electrical spikes.

2. 2

   Access the DEF Pump

   Locate the DEF pump module (Urea supply box), typically mounted near the DEF tank.

3. 3

   Repair Wiring

   If your diagnostic checks revealed a short to ground in the harness, repair the damaged wire using OEM-approved heat-shrink connectors and re-loom the harness to prevent future chafing.

4. 4

   Replace the Sensor/Pump Module

   If the short is internal to the sensor, remove the DEF lines (be prepared for minor fluid spillage) and unbolt the pump module.

5. 5

   Install New Component

   Mount the new DEF pump module, reconnect the DEF lines securely, and plug in the electrical connector.

6. 6

   Clear Codes and Test

   Turn the battery switch back on. Connect a diagnostic scan tool (like the CNH Electronic Service Tool) to clear the inactive 19048 / P204C codes. Start the engine and allow the SCR system to build pressure to verify the repair.