New Holland NH 3108 – Engine Control Unit (ECU / EDC / Engine Controller): CC HS Power stage 1 fuel press. Control - SOURCE LOW

This fault code indicates a Short Circuit to Ground on the High-Side (HS) power stage 1 circuit that controls the fuel pressure metering unit. The metering unit regulates the amount of fuel entering the high-pressure fuel pump (CP3). When the controller detects that the voltage on this circuit is pulled low (shorted to ground), it logs this code and will typically trigger an engine derate or shutdown to protect the system.

• New Holland T5.95
• New Holland T5.105
• New Holland T5.115
• New Holland T6 Series
• New Holland T7.175
• New Holland T7.190
• New Holland T8 Series

1. 1

   Visually inspect the wiring harness routing between the Engine ECU and the fuel pressure metering unit for chafed wires rubbing against the engine block or brackets.

2. 2

   Disconnect the plug at the fuel pressure metering unit and check for water ingress, corrosion, or melted/pushed pins.

3. 3

   Perform a harness short-to-ground test by disconnecting the Engine ECU and metering unit connectors, then checking continuity between the metering unit control wires and chassis ground.

4. 4

   Measure the resistance across the pins of the fuel pressure metering unit to check for an internal dead short.

1. 1

   Disconnect Power

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

2. 2

   Isolate the Fault

   Perform the diagnostic checks above to isolate whether the short is in the wiring harness or the component itself.

3. 3

   Repair the Harness (If Applicable)

   If the multimeter test reveals a short to ground in the harness, trace the wire back to the ECU. Repair the chafed section of the wire using proper soldering and heat-shrink tubing, or replace the damaged pigtail connector.

4. 4

   Replace the Metering Unit (If Applicable)

   If the harness tests good but the metering unit is internally shorted: Clean the area around the high-pressure fuel pump (CP3) thoroughly to prevent dirt from entering the fuel system. Remove the retaining screws holding the fuel pressure control valve to the pump. Carefully extract the valve. Lubricate the O-rings on the new valve with clean diesel fuel and install it into the pump. Torque the fasteners to OEM specifications.

5. 5

   Reassemble and Clear Codes

   Reconnect all electrical connectors and the battery. Use a diagnostic tool (such as the New Holland EST or a compatible CAN-bus DTC eraser) to clear the inactive 3108 fault code from the Engine ECU.

6. 6

   Test Run

   Start the engine and verify that the fuel pressure tracks the commanded pressure without throwing the code.