Case IH 19082 – DCU (Dosing Control Unit): Voltage supply 3 - Coolant control valve and reverting valve (UB3) electrical | Short to bat at UB3 with Key 15 off

The system has detected a short to battery (unintended high voltage) on the UB3 voltage supply circuit when the ignition key is turned off (Key 15 off). This circuit powers the Reverting Valve and the Coolant Control Valve.

• Tier 4a
• Tier 4b
• Magnum 235
• Magnum 250
• Magnum 280
• Magnum 315
• Magnum 340 (Series 4)
• Steiger 350 through 600
• Puma Series
• Maxxum Series
• Austoft 9000 series
• Austoft 9900 series

1. 1

   Visually inspect the wiring harness running from the DCU to the DEF Supply Module and the Coolant Control Valve for chafed wires shorting to a 12V power source.

2. 2

   Disconnect harnesses at the DEF pump module and DCU to check for water intrusion, DEF crystallization, or bent/corroded pins that could bridge circuits.

3. 3

   With the key off (Key 15 off), use a multimeter to test the UB3 voltage supply pin at the valve connectors. If voltage is present, trace the wire back to find the short to power.

4. 4

   Disconnect the Coolant Control Valve and the DEF Supply Module one at a time. If the short circuit status changes to an open circuit (Code 19083 / P20A0), the internal solenoid of the unplugged component is shorted.

1. 1

   Disconnect Power

   Turn off the battery disconnect switch to ensure the system is completely powered down.

2. 2

   Repair Wiring

   If the diagnostic tests revealed a short in the wiring harness, repair the damaged section of the wire using OEM-approved heat-shrink connectors, or replace the affected harness section.

3. 3

   Replace the Coolant Control Valve

   If faulty, drain a small amount of engine coolant. Disconnect the electrical connector and the coolant hoses from the valve. Remove the retaining hardware, install the new valve, and reconnect the hoses and wiring.

4. 4

   Replace the DEF Supply Module / Pump

   If the reverting valve is faulty, clean the area around the DEF pump module. Disconnect the DEF suction, pressure, and backflow lines. Disconnect the main electrical harness. Unbolt the module from its mounting bracket and install the replacement unit.

5. 5

   System Prime and Test

   Reconnect battery power and clear the fault codes using the Case IH Electronic Service Tool (EST). Run an SCR system test / DEF purge test via the diagnostic tool. Verify that the system builds pressure (approx. 9.0 bar / 130.5 psi) and that during the shutdown purge cycle, the reverting valve activates and system pressure drops to 0.2 bar (3.6 psi) within 40 seconds.