New Holland ENG 3138 – Engine Control Module (ECM / ECU): Metering Unit - Temperature Too High or Metering Unit Signal Is Not Plausible

The Fuel Metering Unit on the high-pressure fuel pump is registering an excessively high temperature or an implausible electrical signal, indicating a problem with the regulation of fuel entering the high-pressure pump.

• New Holland T7 series (T7040, T7060)
• New Holland T8 series (T8.xxx)
• New Holland B-Series backhoes (B90B, B110B, B115B)
• New Holland Wheel Loaders (W170B, W190B)
• New Holland Combines/Harvesters (CR9090, CX8080, CX8090 Elevation)

1. 1

   Check the wiring harness between the Engine ECU and the Fuel Metering Unit for loose contacts, chafing, or open/short circuits.

2. 2

   Verify that the ECU is sending the correct pulse-width modulated (PWM) signal and voltage to the metering unit.

3. 3

   Verify that the rail pressure sensor is reading accurately. An inaccurate rail pressure sensor or a defective high-pressure pump can cause the metering unit to overwork and overheat.

4. 4

   Ensure that the metering unit reflux (return flow) is not too low, which can cause temperature buildup.

1. 1

   Safety First

   Turn off the engine, remove the key, and allow the engine and fuel system to cool down. High-pressure fuel systems are dangerous when pressurized and hot.

2. 2

   Inspect the Harness

   Locate the Fuel Metering Unit on the back of the Bosch high-pressure fuel pump. Disconnect the electrical connector and inspect the pins for corrosion, melting, or pushed-out terminals.

3. 3

   Test the Circuit

   Using a multimeter, test the continuity of the wires from the metering unit connector back to the Engine ECU harness. Repair any damaged wiring.

4. 4

   Replace the Metering Unit

   If the wiring and ECU power stage are intact, the Fuel Metering Unit itself has likely failed internally. Clean the area around the metering unit, remove the mounting screws, and discard the old O-rings. Lubricate the O-rings on the new metering unit with clean diesel fuel, carefully install it into the pump, and torque the fasteners to OEM specifications.

5. 5

   Clear Codes and Test

   Reconnect the electrical harness. Use a CNH EST (Electronic Service Tool) or compatible diagnostic scanner to clear the ENG 3138 fault code. Prime the fuel system, start the engine, and monitor the fuel rail pressure and metering unit parameters to ensure the issue is resolved.