Case IH 3047 – Engine Control Module (ECM / EDC): Main Relay 2 Failure _Short circuit to Battery

The engine controller has detected that the control circuit for Main Relay 2 (or the high-pressure fuel pump relay) is receiving unintended battery voltage, indicating a short circuit to a power source.

• Case IH Magnum Series (235-340 Series 4)
• Case IH Puma Series (140, 165, 180, 195, 210, 225)
• Case IH Steiger Series
• Case IH Axial-Flow Combines (7230, 8230, 9230, 7240)
• Case Construction Equipment (580 Super N backhoes, CX-series excavators)

1. 1

   Identify the Relay: Locate 'Main Relay 2' (or the High Pressure Pump Relay) in the machine's main relay/fuse panel.

2. 2

   Relay Inspection: Remove the relay and inspect the pins and socket for corrosion, melting, or signs of arcing.

3. 3

   Wiring Harness Check: The primary cause of this code is a wiring issue. Use a multimeter to check the control wire running from the Engine ECM to the relay socket. Test for continuity to battery power (a short to battery).

4. 4

   Component Testing: Swap the relay with a known good relay of the same type (e.g., a lighting or horn relay) to see if the fault code changes or clears. If it does, the relay itself has an internal short.

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the negative battery cable to protect the ECM.

2. 2

   Isolate the Short

   If the relay swap test proved the relay was good, trace the wiring harness from the relay panel back to the Engine ECM.

3. 3

   Repair Wiring

   Look for areas where the wiring harness may have rubbed against the chassis, engine block, or other hot/moving components, causing the insulation to melt and the wire to touch a 12V power source. Splice and repair the damaged wire using weather-sealed connectors.

4. 4

   Replace the Relay

   If the relay was internally shorted, install a new OEM replacement relay.

5. 5

   Reassemble and Clear Codes

   Reconnect the battery, turn the key to the ON position, and use a diagnostic tool (like the CNH Electronic Service Tool) to clear the inactive 3047 fault code.

6. 6

   Test

   Start the engine and verify that the code does not return and that the engine runs without derating.