Case IH 19173 (DTC 627A) - ECU – Engine Control Unit (ECU / ENG): DEF/AdBlue dosing valve actuator short circuit in high side failure

The control module has detected a short circuit to battery voltage on the high-side power supply circuit of the Diesel Exhaust Fluid (DEF) dosing valve (also known as the DEF injector). When this circuit shorts, the actuator cannot properly meter DEF into the exhaust stream, which triggers an SCR (Selective Catalytic Reduction) system failure and will result in an engine power loss or derate.

• MAXXUM T4E
• Case IH 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Case IH 250 Series Axial-Flow Combines (8250)

1. 1

   Inspect the wiring harness between the Engine ECU and the DEF dosing valve for chafed insulation, melted wires, or pinch points (wiring short cause).

2. 2

   Disconnect the DEF dosing valve and inspect the pins for corrosion, moisture intrusion, or bent terminals.

3. 3

   With the ECU and dosing valve disconnected, test the high-side supply wire for continuity to battery power using a multimeter.

4. 4

   If the wiring harness is intact and no voltage is present on the disconnected supply wire, the short is likely internal to the DEF dosing valve actuator (component failure cause).

1. 1

   Turn off the machine and disconnect the battery to prevent further electrical damage.

2. 2

   If the multimeter test revealed a harness issue, repair or replace the damaged section of the wiring harness.

3. 3

   If the harness is good, proceed to replace the DEF dosing valve.

4. 4

   Disconnect the electrical connector and the DEF fluid supply line from the DEF dosing valve.

   (Note: Be prepared for minor DEF spillage. Clean any spilled DEF immediately with warm water, as it is corrosive to metal).

5. 5

   Unbolt the DEF dosing valve from its mounting point on the exhaust/SCR mixing pipe.

6. 6

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

   Torque the mounting hardware to OEM specifications.

7. 7

   Reconnect the DEF supply line and the electrical connector.

8. 8

   Reconnect the battery.

9. 9

   Use a diagnostic tool (such as the Case IH EST or a compatible scanner like TEXA) to clear the fault codes.

10. 10

    Run an 'AdBlue/DEF dosing valve control test' (UDVC) via the diagnostic tool, or run the machine under load to verify the SCR system is functioning normally and the code does not return.