Case IH 19074 – DCU (Dosing Control Unit): Short Circuit to Ground on Voltage supply 2 - tube heaters (UB2) electrical

Indicates a Short Circuit to Ground (or open circuit) on the Voltage supply 2 - tube heaters (UB2) electrical circuit, pointing to an electrical failure in the DEF/AdBlue Suction Line Heater Actuator powerstage. This prevents the heater from thawing DEF fluid in cold conditions, leading to an SCR system failure and engine derate.

• Tier 4b
• Magnum Series 235
• Magnum Series 260
• Magnum Series 290
• Magnum Series 315
• Magnum Series 340
• Steiger Series 350
• Steiger Series 400
• Steiger Series 450
• Steiger Series 500
• Steiger Series 550
• Steiger Series 600
• Rowtrac Series 350
• Rowtrac Series 400
• Axial-Flow Combine 7230
• Axial-Flow Combine 8230
• Axial-Flow Combine 9230

1. 1

   Check the engine and emissions wiring harness connecting the DCU to the DEF suction line heater for chafing, bare wires, or pinched areas that could cause a short to ground.

2. 2

   Disconnect the DEF suction line heater and test the resistance across the heater pins with a multimeter to check for an internal short within the heater itself.

3. 3

   Check the UB2 (Voltage supply 2) pins at the DCU connector for proper voltage and continuity to ground.

4. 4

   Verify if the fault is active. If inactive, clear the code using the Electronic Service Tool and run the machine to see if it returns.

1. 1

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

   Ensure the machine is fully powered down before beginning repairs.

2. 2

   Locate the DEF/AdBlue Dosing Control Unit (DCU) and trace the wiring to the DEF suction line heater.

   Follow the harness to inspect the physical condition of the wiring.

3. 3

   Repair the wiring harness if damaged.

   If the wiring harness is damaged and shorting to the chassis, repair the broken wires and re-loom the harness securely away from vibration points.

4. 4

   Replace the DEF suction line heater/hose assembly.

   If the wiring is intact but the suction line heater tests faulty (internal short), replace the assembly.

5. 5

   Replace the Dosing Control Unit (DCU).

   If the internal tube heater electrical failure is traced back to a burnt powerstage inside the module itself, you must replace the DCU.

6. 6

   Remove the defective DCU and install the replacement module.

   Physically swap the faulty DCU with the new unit.

7. 7

   Perform software calibration.

   Use the Case IH Electronic Service Tool to flash the correct firmware and passwords for the specific machine, as CNH will not issue passwords unless troubleshooting has been properly performed.