New Holland ENG 3048 – Engine Control Module (ECM): Main Relay 2 Failure — Short circuit to Ground

The Engine Control Module (ECM) has detected that the control circuit for Main Relay 2 is shorted to ground. This means voltage is taking an unintended path to the chassis/ground before reaching or properly passing through the relay, which can prevent the relay from energizing or cause a blown fuse.

• T7 Series (T7.220, T7.235, T7.250, T7.260, T7.270)
• T8 Series
• T6000 Series (T6010–T6070)
• B110B Tractor Loader Backhoe
• Magnum 235–340 (Series 4)
• 580 Super N Backhoe

1. 1

   Visually inspect the wiring harness between the ECM and the fuse/relay box for chafed insulation, pinched wires, or areas rubbing against the engine block or chassis

2. 2

   Remove Main Relay 2 and test it with a multimeter for an internal short circuit across the coil pins

3. 3

   With the relay removed and the battery disconnected, use a multimeter to check for continuity to ground on the ECM control wire

4. 4

   Verify the alternator is outputting the correct voltage, as a defective voltage governor can trigger related relay codes

1. 1

   Disconnect Power

   Always disconnect the negative battery terminal before servicing ECM wiring or relays.

2. 2

   Resolve Wiring Shorts

   If a short to ground was found in the harness during diagnostics, repair the damaged section of the wire using weather-sealed heat shrink connectors, or replace the affected harness section.

3. 3

   Replace the Relay

   If Main Relay 2 failed the internal resistance test, replace it with a new OEM relay.

4. 4

   ECM Replacement

   If the wiring harness is completely intact and the relay is functional, the short to ground is likely internal to the ECM. Replace engine controller.

5. 5

   Reassembly and Clearing

   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 fault codes. Start the engine to verify the code does not return.