Case IH 3764 – Engine Control Unit (ECU): ECU after run power interruption

The Engine Control Unit (ECU) lost power prematurely during its 'after-run' phase. The after-run phase is the period immediately after the ignition key is turned off, during which the ECU remains powered to save operating data and perform critical shutdown procedures, such as reversing the DEF/AdBlue dosing pump to evacuate fluid.

• Steiger T4B
• 230 Series Axial-Flow Combines (7230, 8230, 9230)
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• A8810 Sugarcane Harvesters
• Magnum
• Maxxum
• T-Series
• TR340B
• TV370B

1. 1

   Verify Operator Procedure: Check if the operator is turning off the master battery disconnect switch immediately after turning off the ignition key. The operator must wait at least 90 seconds before throwing the disconnect switch.

2. 2

   Check the ECU Main / After-Run Relay: Locate the ECU Main Relay and the After-Run Relay in the power distribution box. Test the relay to ensure it is not dropping out early or suffering from internal high resistance.

3. 3

   Inspect Fuses: Check the auxiliary relay fuses (often a 5A or 25A mini fuse) that supply constant battery voltage to the ECU for the after-run cycle.

4. 4

   Harness and Ground Check: Inspect the wiring harness between the battery disconnect switch, the auxiliary relay fuse, and the ECU for an open circuit, loose ground, or a faulty emergency stop (eStop) device.

1. 1

   Educate the Operator

   If the diagnostic checks confirm the machine is mechanically sound, instruct the operator on proper shutdown procedures. The battery disconnect switch must not be turned off until the DEF system has finished purging (listen for the DEF pump to stop running, usually 1.5 minutes after key-off).

2. 2

   Disconnect Battery

   If a hard part has failed, ensure the ignition is off, wait the full 90 seconds for the after-run to complete, and then turn off the master battery disconnect switch.

3. 3

   Replace Faulty Relays/Fuses

   If the ECU Main Relay or After-Run Relay failed testing, pull the faulty relay from the fuse block. Inspect the female terminal cavities for pushed-out pins, corrosion, or heat damage. Replace the relay and any blown fuses.

4. 4

   Repair Wiring (If Applicable)

   If an open circuit was found in the application supply harness, repair the wire using OEM-approved weather-sealed splices.

5. 5

   Clear Codes

   Reconnect battery power, turn the key to the ON position, and use your diagnostic tool to clear the inactive 3764 / F561 fault code. Perform a standard key-cycle (ON, run briefly, OFF, wait 2 minutes) to verify the code does not return.