Case IH 19172 – DCU (Dosing Control Unit): Cooling control valve short circuit to ground | P20A2 Vent valve (Reductant Purge Control Valve) - short circuit low

The controller has detected an electrical short to ground in the circuit operating the DEF (Diesel Exhaust Fluid) cooling control valve (also referred to as the reductant purge control valve or reverting valve). Because of the short, the circuit voltage is being pulled below the acceptable lower limit.

• Tier 4a
• Case IH Magnum Series: 235, 260, 290, 315, 340, 370 (Series 4)
• Case IH Steiger Series: 350, 400, 450, 500, 550, 600
• Case IH Puma Series

1. 1

   Visually inspect the wiring harness connecting the DCU to the DEF Urea Supply Module for rubbing against the frame or DEF fluid creep/crystallization at the connectors.

2. 2

   Test the circuit for a short to ground by disconnecting the harness from the DCU and DEF supply module, and probing the control terminals (e.g., Pin 11 and Pin 12) for continuity to a known good metallic ground.

3. 3

   If the wiring harness tests good (no continuity to ground), suspect an internal short in the Reductant Purge Control Valve / Urea Supply Module.

1. 1

   Power Down

   Turn off the machine and disconnect the battery to prevent electrical spikes during the repair.

2. 2

   Clean the Area

   Clean the work surface and the exterior of the DEF supply module thoroughly to prevent dirt or crystallized DEF from contaminating the system.

3. 3

   Harness Repair (If Applicable)

   If the diagnostic test revealed a short in the wiring, locate the chafed wire, repair it using OEM-approved weather-sealed connectors, and re-loom the harness to prevent future rubbing.

4. 4

   Valve / Module Replacement

   If the wiring is intact, the fault lies within the valve. Disconnect the electrical connector and the fluid lines from the cooling control valve / reductant purge control valve on the Bosch Denoxtronic supply module.

5. 5

   Installation

   Install the replacement valve or supply module. Ensure all O-rings and seals are seated properly to prevent DEF leaks, which will cause future electrical shorts due to fluid creep.

6. 6

   Clear Codes

   Reconnect the battery, use an Electronic Service Tool to clear the 19172 / P20A2 fault code from the DCU, and run a dosing system test to verify the repair.