Case IH 19181 – DCU (Dosing Control Unit): Reverting valve electrically | Short circuit to battery | P20A3 Vent valve (Reductant Purge Control Valve) - short circuit high

The engine's aftertreatment system has detected a high voltage short (short circuit to battery) on the electrical circuit controlling the reductant purge control valve (reverting valve or 4-2 way valve).

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

1. 1

   Disconnect the electrical connector to the UREA (DEF) pump module to isolate the short.

2. 2

   Turn the key ON and monitor fault codes: if the code changes from 19181 to 19183 (Open load / Open circuit), the short is internal to the UREA pump module.

3. 3

   If the fault code remains 19181, the short circuit to battery voltage is located in the machine's main wiring harness between the DCU and the pump module.

4. 4

   Inspect the wiring harness from the DCU to the DEF pump module for melted insulation, chafing, or pinched wires bridging the reverting valve signal wire to a 12V/24V power source.

1. 1

   Power Down

   Turn off the machine and disconnect the battery ground to ensure safety while working on the electrical system.

2. 2

   Isolate the Short

   Perform the diagnostic disconnect test (disconnecting the UREA pump module) to determine if the short is in the module or the harness.

3. 3

   Replace the Faulty Component

   If the short is in the module: Remove the DEF lines and electrical connectors from the UREA pump module, unbolt it from its mounting bracket, and install the replacement module. If the short is in the harness: Repair the damaged section of the wiring harness using appropriate weatherproof splices, or replace the affected harness section entirely.

4. 4

   Reassemble and Prime

   Reconnect all DEF lines (ensuring no kinks) and electrical connectors.

5. 5

   Clear and Test

   Reconnect the battery, clear the inactive fault codes using a diagnostic tool, and run a UREA Dosing System Test (UDST) or allow the engine to run and cycle a purge event to verify the reverting valve operates without throwing a high-voltage code.