Case IH 19037 – DCU (Dosing Control Unit): Sensor supply 2 (5V internal; for UREA pressure sensors) — Supply Voltage too high / P204D Reagent-pressure sensor-short circuit high.

The system utilizes a 5-volt reference circuit to power the UREA (DEF) pressure sensor. This code triggers when the control module detects that the voltage on this 5V supply circuit is too high (exceeding the normal 5V threshold). This typically indicates a "short to power" (e.g., the 5V wire is shorted to a 12V battery source), a failed pressure sensor internally shorting the circuit, or a failure within the control module itself.

• Tier 4a
• Case IH Magnum Series (235 - 340, Series 4)
• Case IH Steiger Series (350 - 600 HP)
• Case IH Puma Series

1. 1

   Visual Inspection: Inspect the wiring harness running from the DCU to the DEF supply module (pump) for chafing, melting, or pinched wires that could cause the 5V sensor wire to short against a 12V power wire.

2. 2

   Connector Check: Disconnect the harness at the DEF pump module. Check the connector terminals for water ingress, debris, or corrosion (which can bridge pins and cause a short).

3. 3

   Voltage Test: With the sensor unplugged and the key ON, use a multimeter to measure the voltage at the 5V supply pin on the harness side. If it reads 12V (battery voltage), the short is in the wiring harness. If it reads a steady 5V, the short is likely internal to the DEF pressure sensor/pump module.

4. 4

   Module Reset: Disconnect the tractor's battery for a short period to reset the electronic control systems and clear temporary DCU glitches.

1. 1

   Prep the Machine

   Turn off the engine, remove the key, and disconnect the battery.

2. 2

   Locate the Module

   Locate the DEF supply module (dosing pump), which is typically mounted near the DEF tank or on the frame rail.

3. 3

   Disconnect Electrical

   Unplug the main electrical harness connector from the DEF supply module.

4. 4

   Disconnect Fluid Lines

   Carefully disconnect the DEF inlet and outlet lines. Note: DEF is highly corrosive to metals and plastics. Clean up any spills immediately with warm water.

5. 5

   Remove the Module

   Unbolt the mounting hardware securing the DEF supply module to its bracket and remove the unit.

6. 6

   Install the New Part

   Mount the replacement DEF supply module/sensor assembly and secure the bolts.

7. 7

   Reconnect

   Reattach the DEF fluid lines (ensure they click/lock into place) and plug in the electrical harness.

8. 8

   Clear Codes

   Reconnect the battery, turn the key to the ON position, and use a diagnostic scan tool to clear the 19037 / P204D fault code from the DCU. Run the machine to verify the code does not return.