Case IH 3139 – Engine Control Module (ECM) / EDC: Metering Unit Signal Range Check - Signal Too High

The Engine Control Module (ECM) monitors the electrical circuit of the Fuel Metering Unit located on the high-pressure fuel pump. This code triggers when the voltage or current feedback from the metering unit circuit is above the maximum expected threshold, typically indicating a short to battery voltage in the wiring harness, high circuit resistance, or an internal electrical failure (short) within the metering unit's solenoid.

• skid steer
• Magnum 235 - 340 (Series 4)
• Steiger Series
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)

1. 1

   Inspect the wiring harness and connectors between the Engine Control Module (EDC) and the Fuel Metering Unit on the high-pressure fuel pump for chafed wires, melted insulation, or damaged connector pins.

2. 2

   Disconnect the metering unit and use a multimeter to check the harness side for a short to battery voltage.

3. 3

   Measure the internal resistance across the pins of the Fuel Metering Unit itself and compare against the specific FPT engine manual's specifications to confirm if the solenoid has failed internally.

4. 4

   Look for accompanying fuel system codes (such as 3140 for Signal Too Low, or 3141 for Fuel Flow Setpoint Too Low) to help isolate whether the issue is purely electrical or related to physical fuel pressure.

1. 1

   Preparation

   Park the machine on a level surface, turn off the engine, remove the key, and disconnect the negative battery cable to prevent electrical arcing or accidental ECU damage.

2. 2

   Locate the Component

   Locate the high-pressure fuel pump on the engine block. The Fuel Metering Unit is bolted directly to the body of this pump.

3. 3

   Clean the Area

   Thoroughly clean the metering unit and the surrounding area on the fuel pump with brake cleaner or a suitable solvent. The common-rail fuel system is highly sensitive to contamination; no dirt must enter the pump housing.

4. 4

   Disconnect

   Unplug the electrical connector from the Fuel Metering Unit.

5. 5

   Removal

   Remove the mounting fasteners (usually Torx or Allen screws) securing the metering unit to the pump. Carefully pull the unit straight out. Ensure the old O-rings come out with the unit and are not left inside the pump bore.

6. 6

   Installation

   Lubricate the O-rings on the new Fuel Metering Unit with clean diesel fuel. Carefully insert the new unit into the pump housing, ensuring it seats squarely without pinching the O-rings.

7. 7

   Torque

   Install the mounting fasteners and torque them to the OEM specifications outlined for your specific FPT engine model.

8. 8

   Reassembly

   Reconnect the electrical harness to the new metering unit. Reconnect the battery.

9. 9

   Clear Codes and Test

   Turn the ignition on. Use the Case IH Electronic Service Tool (EST) to clear the inactive 3139 fault code. Start the engine, check for fuel leaks around the pump, and verify that the code does not return under load.