Case IH F-1321-04 - ECU – ECU: Starter relay low side driver circuit short to ground failure

The control module has detected that the ground-side control circuit (low side driver) for the starter relay is shorted to ground. This condition typically prevents the ECU from properly controlling the starter relay, which can result in a no-crank/no-start condition or, in rare cases, the starter attempting to engage uncommanded.

• MAGNUM AFS Connect
• Austoft A9900
• 240 Series Axial-Flow Combines

1. 1

   Visually inspect the wiring harness running between the ECU and the starter relay for chafed wires, pinched harnesses, or melted insulation that could cause the low-side driver wire to touch the chassis (ground).

2. 2

   Disconnect the harness at both the ECU and the starter relay, then use a multimeter to check for continuity between the low-side control wire and chassis ground. If continuity exists, the wire is shorted.

3. 3

   Test the starter relay itself. An internal short inside the relay coil can sometimes pull excessive current or ground out the circuit, triggering the driver fault.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the negative battery cable to prevent accidental shorts or starter engagement.

2. 2

   Access the Relay and ECU

   Locate the main electrical distribution box where the starter relay is housed, and locate the Engine ECU.

3. 3

   Isolate the Short

   Based on your diagnostic checks, locate the exact point of the short to ground in the wiring harness.

4. 4

   Repair the Harness

   If the wire is chafed and grounding out against the chassis, repair the damaged section of the wire using OEM-approved heat-shrink butt connectors, and re-loom the harness to protect it from future abrasion.

5. 5

   Replace the Relay (If Faulty)

   If the wiring tests perfectly fine, the starter relay itself may be internally shorted. Pull the old relay and install a new OEM replacement.

6. 6

   Reassemble and Clear Codes

   Reconnect the battery. Connect a diagnostic tool to the machine, clear the inactive F-1321-04 / 3262 fault code, and cycle the key to verify the engine cranks normally and the code does not return.