Case IH 3507 – Engine Control Unit (ECU A-9000): Engine cranked for too long or key switch failure

The Engine Control Unit has detected that the starter engagement signal circuit (Terminal 50, routed to ECU pin 63) has remained in a "high" (powered) state for an excessive amount of time. This condition occurs either because the operator manually held the key in the crank position for too long or because there is an electrical failure, such as a stuck ignition switch or a short-to-power in the wiring harness.

• Steiger T4B
• Case IH 240 Series Axial-Flow Combines
• Case N-Series Loader Backhoes
• Case IH Magnum Series Tractors (235-340)

1. 1

   Operator Interview / Hard Start Verification: Determine if the machine was recently cranked for an extended period due to running out of fuel, cold weather, or lost prime. If so, the code may just need to be cleared.

2. 2

   Ignition Switch Mechanical Check: Turn the key to the 'Start' position and release it. Ensure the key springs back to the 'Run' position smoothly and does not physically stick in the crank position.

3. 3

   Electrical Circuit Test: Disconnect the harness from the ignition switch and from the ECU A-9000. Use a multimeter to check the wire running to ECU Pin 63 (Terminal 50 circuit) for a short to battery voltage.

4. 4

   Starter Relay Check: Verify that the starter relay is not sticking closed, which can sometimes backfeed voltage to the terminal 50 circuit depending on the machine's specific wiring schematic.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the negative battery cable to prevent accidental cranking or electrical shorts.

2. 2

   Access the Switch

   Remove the steering column covers or dash panel trim required to access the rear of the ignition key switch.

3. 3

   Test the Switch

   With the switch disconnected, use a multimeter to test continuity across the switch terminals. Check the terminal corresponding to the "Start" (Terminal 50) position. If there is continuity to the battery power terminal when the key is resting in the "Run" position, the internal return spring or contacts have failed.

4. 4

   Replace or Repair

   If the switch fails the continuity test, replace the ignition switch. If the switch tests good, locate and repair the short-to-power in the wiring harness between the ignition switch and ECU A-9000 Pin 63.

5. 5

   Reassembly

   Plug the harness back into the ignition switch and the ECU. Reinstall the dash panels.

6. 6

   Clear Codes

   Reconnect the battery. Turn the key to the ON position and use the machine's diagnostic monitor or an electronic service tool to clear the inactive 3507 / 4761 fault code.

7. 7

   Verify Repair

   Start the engine normally. Verify that the starter disengages immediately upon releasing the key and that the fault code does not return.