New Holland 3138 – ECU: Metering Unit - Temperature Too High

The temperature of the fuel metering unit has exceeded its normal operating range. The fuel metering unit, located on the high-pressure fuel pump, regulates the amount of fuel delivered to the fuel rail. The Engine Control Module (ECU) monitors this temperature via a sensor. An abnormally high temperature reading indicates a malfunction or overheating condition in the fuel system, which requires investigation to determine the root cause and prevent further damage or engine performance issues.

• New Holland T8 Series
• T8.275
• T8.300
• T8.330
• T8.360
• T8.390
• New Holland T7 Series
• New Holland T6000 Series
• T6010
• T6020
• T6030
• T6040
• T6050
• T6060
• T6070

1. 1

   Visually inspect the fuel metering unit, connectors, and surrounding wiring harness for damage, corrosion, or loose connections. Ensure the unit is free from external debris that could restrict air circulation.

2. 2

   Check the fuel system for restrictions (which can cause the pump and metering unit to work harder). Inspect for clogged fuel filters or blockages in the fuel lines leading to the high-pressure pump.

3. 3

   Perform electrical testing on the metering unit's temperature sensor (thermistor). Disconnect the harness and measure resistance across the pins; it should not read infinite (open circuit) or zero (short circuit).

4. 4

   Check the wiring harness for continuity and for shorts to ground or power (the sensor is typically supplied with a 5-volt reference from the ECU).

5. 5

   Review other active or stored fault codes (e.g., 3139, 3140) for related fuel pressure or metering unit signal faults that could provide diagnostic clues.

1. 1

   Address fuel system issues

   If clogged filters or fuel line restrictions are found, replace the filters and clear any blockages. Bleed the fuel system and operate the machine to see if the fault code returns.

2. 2

   Repair wiring

   If wiring faults such as breaks, corrosion, or shorts are identified during testing, repair or replace the affected section of the harness. Ensure all connections are clean and secure.

3. 3

   Replace the fuel metering unit

   If the diagnostic checks point to an internal failure of the metering unit itself (e.g., incorrect resistance readings), replace the unit. Disconnect the battery, thoroughly clean the area around the high-pressure pump and metering unit, and disconnect the electrical connector. Unscrew the mounting bolts, carefully remove the old unit, and ensure the sealing O-rings are also removed. Lubricate the O-rings on the new metering unit with clean diesel fuel or a suitable lubricant, install the new unit, and tighten the mounting bolts to the manufacturer's specified torque. Reconnect the electrical connector and re-engage the battery. Prime the fuel system and start the engine to check for leaks and verify the fault is cleared.