Case IH 3268 – Engine Control Unit (ECU): Main relay 3 _Short circuit to Ground

The Engine Control Unit (ECU) has detected that the voltage on the circuit controlled by Main Relay 3 has dropped to zero, indicating the power wire is touching the chassis or a ground source, or the relay itself has failed internally. To protect the system, the ECU will automatically shut off the relay.

• Case IH Magnum Series (235, 260, 290, 315, 340 Series 4)
• Case IH Steiger Series
• Case IH Puma Series
• Case IH Maxxum Series

1. 1

   Locate the main relay panel and identify Main Relay 3 (often labeled as the Fuel Filter Heater Relay or A/C Compressor Relay)

2. 2

   Perform a relay swap test by exchanging it with a known good relay of the exact same type from the fuse box to see if the code clears

3. 3

   Inspect the wiring harness running from the ECU to Main Relay 3, and from the relay to the fuel filter heater element for rubbed-through insulation, pinched wires, or melted loom

4. 4

   Disconnect the fuel filter heater element; if the fault changes to an 'Open Load' fault (Code 3168), the heater element itself is internally shorted

5. 5

   Inspect the high/low power output pins on the ECU for corrosion, moisture, or bent pins

1. 1

   Disconnect Power

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

2. 2

   Access the Relay Panel

   Open the cab fuse/relay panel or the engine compartment power distribution box (location varies by tractor series).

3. 3

   Test the Circuit

   Using a digital multimeter, test the load wire going from the relay socket to the fuel filter heater for continuity to ground.

4. 4

   Repair Wiring (If Applicable)

   If continuity to ground is found on the power wire, trace the harness and repair the chafed/shorted section using heat-shrink connectors and new wire loom.

5. 5

   Replace the Relay

   If the wiring and the heater element test fine, the relay's internal FET transistor has likely failed. Plug a new OEM relay into the Main Relay 3 slot.

6. 6

   Reassemble and Clear Codes

   Reconnect the battery. Turn the key to the ON position. Use the tractor's diagnostic display or an electronic service tool to clear the inactive fault codes. Start the engine and verify that code 3268 does not return.