New Holland NH 3113 – Engine Control Unit (ECU): Main relay defect - ABOVE NORMAL

The Engine Control Unit (ECU) has detected a short-to-high-source (battery voltage) condition in the circuit that supplies power to the fuel metering unit on the high-pressure fuel pump.

• T7 Series
• T7.220
• T7.235
• T7.250
• T7.260
• T7.270
• T8 Series
• T6000 Series
• TS-A Series
• CR9090
• CX8080 Elevation
• CX8090 Elevation

1. 1

   Visually inspect the wiring harness from the Engine ECU to the fuel metering unit for chafed insulation, melted wires, or pinch points shorting to a live wire

2. 2

   Disconnect the electrical connector at the fuel metering unit, turn the key ON, and check for improper voltage on the ECU-controlled circuit

3. 3

   Test the internal resistance of the fuel metering unit solenoid to ensure it has not internally shorted

4. 4

   Disconnect the ECU harness and check for continuity to battery positive on the pins dedicated to the fuel metering unit to isolate the short

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the battery to prevent further electrical damage during testing.

2. 2

   Isolate the Short

   Disconnect the fuel metering unit on the CP3 pump.

3. 3

   Repair Wiring

   If the diagnostic checks reveal a short to battery voltage in the wiring harness, open the wire loom, locate the compromised wire, and repair it using OEM-approved splicing techniques (solder and heat shrink).

4. 4

   Replace Metering Unit

   If the wiring harness tests perfectly but the fuel metering unit is internally shorted, remove the unit from the high-pressure pump (usually held by a few Torx screws) and install a new one. Lubricate the O-rings on the new unit with clean diesel fuel before installation.

5. 5

   Address ECU Failure

   If the wiring and metering unit are both good, the ECU itself has failed. The ECU will need to be removed and sent to a specialist for internal repair, or replaced entirely and flashed with the correct data set using the New Holland Electronic Service Tool (EST).

6. 6

   Clear Codes

   Reconnect all components, power up the machine, and use the EST to clear the inactive fault codes. Run the engine to verify the repair.