Case IH 3048 – Engine Control Module (ECM): High pressure pump relay - short circuit to ground

The control module has detected a short to ground in the electrical circuit responsible for energizing the high-pressure fuel pump relay or main engine relay 2.

• Magnum Series (235 - 340 Series 4)
• Puma Series (140, 165, 180, 195, 210, 225, CVX)
• Steiger Series
• Farmall Series
• 580 Super N
• 621C Loaders

1. 1

   Verify battery voltage is within normal parameters, as voltage irregularities can trigger relay faults.

2. 2

   Locate Main Relay 2 / High Pressure Pump Relay in the power distribution box and swap it with a known good relay of the same type.

3. 3

   Probe the wiring harness between the ECM and the relay block, checking for continuity and specifically testing for a short to ground on the low side of the relay control circuit.

4. 4

   Inspect the ECM connectors for bent pins, moisture, or corrosion that could bridge the relay circuit to a ground pin.

1. 1

   Disconnect Power

   Disconnect the negative battery cable before servicing the engine electrical system to prevent further shorts.

2. 2

   Replace the Relay

   If the diagnostic checks point to an internally shorted relay, remove the defective High Pressure Pump Relay / Main Relay 2 and install a new OEM replacement.

3. 3

   Repair the Harness

   If a short to ground was found in the wiring (e.g., chafed wire rubbing against the engine block or chassis), cut out the damaged section, solder in a new wire, and seal it with heat-shrink tubing. Reroute the harness or add protective loom to prevent recurrence.

4. 4

   Replace the Engine Controller

   If the relay and wiring are perfectly intact but the short to ground is internal to the module's driver, replace the engine controller.

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 3048 code. Run the engine to verify the code does not return.