Case IH 3059 (F-1485-07) - ECU – Engine Control Unit (ECU / ECM): Main relay stuck error / ECM After run was Interrupted

The main power relay that supplies voltage to the Engine Control Unit (ECU) has failed in the closed position (stuck closed). Because the relay is stuck, Terminal 30 continues to supply battery power to the ECU even after the ignition key is turned off. This prevents the ECU from properly shutting down, interrupting its programmed 'after-run' sequence.

• VESTRUM CVX
• Magnum 235 - 340 (Series 4)
• Farmall series (e.g., 115U, 40-45-50 CVT)
• Steiger series
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)

1. 1

   Verify if the battery power was manually disconnected (e.g., via a battery disconnect switch) before the ECM was allowed to finish its shutdown sequence (false code cause)

2. 2

   Locate the Engine Controller Main Relay and bench test for continuity across the load terminals (Terminal 30 and 87) without power applied to the coil (stuck relay cause)

3. 3

   Inspect the wiring harness between the relay block and the ECU for a short circuit to battery that could bypass the relay and keep the ECU energized (wiring short cause)

4. 4

   If the relay and wiring are functioning correctly, check for an internal ECU hardware failure keeping the circuit energized (internal ECU failure cause)

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the negative battery cable to prevent electrical shorts.

2. 2

   Locate the Relay

   Access the main fuse and relay box (often located in the cab or engine bay firewall, depending on the model). Identify the 'Engine Control Unit (ECU) Permanent battery power supply' relay or 'Cab Main Relay Module'.

3. 3

   Replace the Relay

   If the relay failed the bench test (stuck closed), remove the faulty relay and install a new OEM replacement, ensuring the pin configuration (4-pin or 5-pin) and amperage match.

4. 4

   Repair Wiring

   If the relay was fine but a short was found in the Terminal 30 circuit, repair or replace the damaged section of the wiring harness.

5. 5

   Reassemble and Clear Codes

   Reconnect the battery, turn the key to the ON position, and use a diagnostic tool (like the CNH EST) to clear the inactive 3059 fault code.

6. 6

   Verify Repair

   Start the engine, let it run for a minute, and turn the key off. Wait for the ECU to complete its after-run sequence (usually 30-60 seconds) to ensure the relay clicks off and the code does not return.