Case IH 19173 – Engine Control Unit (ECU) / Engine Aftertreatment Control Module: DEF/AdBlue dosing valve actuator short circuit to battery in high side failure

The engine's aftertreatment control system has detected that the voltage on the high-side control circuit of the DEF (Diesel Exhaust Fluid) dosing valve is abnormally high. This indicates that the circuit is shorted directly to a battery voltage source, preventing the system from properly controlling the injection of DEF into the exhaust stream.

• Tier 4b
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Farmall series (80N, 90C, 100C, 110C, 110U, 120C)
• Steiger tractors
• Magnum tractors

1. 1

   Trace the wiring harness from the DEF dosing valve back to the ECU. Look for chafing, pinched wires, or melted insulation that could cause the high-side wire to short against a 12V/24V power supply wire.

2. 2

   Disconnect the DEF dosing valve and check the connector for DEF fluid intrusion. DEF is highly corrosive and conductive; if it leaks into the connector, it can bridge the pins and cause a short to battery fault.

3. 3

   With the key ON (engine off) and the dosing valve disconnected, use a multimeter to measure the voltage at the harness connector. If battery voltage is present on the control pin when the ECU is not commanding it, the wiring harness is shorted.

4. 4

   Measure the internal resistance across the pins of the DEF dosing valve itself. If the resistance is out of specification or shows a dead short, the actuator inside the valve has failed.

1. 1

   Turn off the machine, remove the key, and disconnect the battery to prevent any further electrical damage.

2. 2

   If the diagnostic checks revealed a shorted wiring harness, repair the damaged section of the wire or replace the affected SCR harness segment.

3. 3

   If the DEF dosing valve is internally shorted or the connector is ruined by DEF intrusion, locate the dosing valve (mounted directly on the exhaust SCR catalyst pipe).

4. 4

   Disconnect the electrical connector and the DEF fluid supply line.

   Note: Be prepared for minor DEF spillage. Clean any spilled DEF immediately with warm water to prevent corrosion.

5. 5

   Remove the mounting bolts securing the dosing valve to the exhaust pipe.

6. 6

   Clean the mounting surface on the exhaust pipe.

7. 7

   Install the new DEF dosing valve using a new mounting gasket/seal to prevent exhaust leaks.

8. 8

   Reconnect the DEF fluid line and the electrical connector.

9. 9

   Reconnect the battery.

10. 10

    Connect a diagnostic tool (such as the Case IH Electronic Service Tool - EST) to clear fault code 19173.

11. 11

    Run a manual DEF dosing test or an SCR system test via the diagnostic tool to prime the system and verify that the valve is actuating correctly without throwing the code.