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F-4377-31 - ECU

Case IH F-4377-31 - ECU – Engine ECU: NH3 sensor signal out of range failure

Issue description

The NH3 (Ammonia) sensor monitors the amount of unreacted ammonia slipping past the Selective Catalytic Reduction (SCR) catalyst. This code triggers when the sensor reports values outside the expected dynamic range, indicating that the sensor has drifted, lost calibration, or failed internally.

Applies to these machines

  • MAGNUM AFS Connect
  • Axial-Flow series (e.g., 240 Series, 6150, 7240, 7250, 8240, 8250, 9240)
  • Magnum
  • Steiger
  • Maxxum
  • Farmall series (e.g., Farmall 110U, Maxxum 115)

Check the cause

  1. Check the presence and correct connection of the NH3 sensor to the CAN network

  2. Inspect the wiring harness and the 8-pin connector going to the NH3 sensor for open circuits, short circuits, or corrosion

  3. Verify the correct functioning of the sensor's CAN controller and ensure it is receiving proper voltage supply

  4. Check the CAN configuration in the downstream NOx sensor, as communication errors can sometimes mimic a drifted sensor

Repair steps

  1. Turn off the machine and disconnect the battery

    to prevent electrical shorts.

  2. Locate the NH3 sensor on the exhaust aftertreatment system

    (typically mounted downstream of the SCR catalyst).

  3. Disconnect the 8-pin electrical harness connector

    from the sensor module.

  4. Carefully unscrew and remove the defective NH3 sensor

    from the exhaust pipe.

  5. Install the new NH3 sensor

    and tighten it to the manufacturer's specified torque.

  6. Reconnect the electrical harness

  7. Reconnect the battery and turn the ignition on

  8. Use the Electronic Service Tool (EST) to clear the F-4377-31 fault code

  9. Run the engine or perform a forced aftertreatment system test

    to verify the new sensor is reading correctly and the code does not return.

Parts you might need

(10)

  • NH3 Sensor / Ammonia Sensor / Aftertreatment Outlet NH3 Gas Sensor

    48188864

    These sensors are typically 8-pin electronic control units designed for FPT Tier 4B / Stage IV emissions systems. Ensure you match the specific cable length (e.g., 700mm vs 1000mm) required for your exact machine model.

  • NH3 Sensor / Ammonia Sensor / Aftertreatment Outlet NH3 Gas Sensor

    48188851

    These sensors are typically 8-pin electronic control units designed for FPT Tier 4B / Stage IV emissions systems. Ensure you match the specific cable length (e.g., 700mm vs 1000mm) required for your exact machine model.

  • NH3 Sensor / Ammonia Sensor / Aftertreatment Outlet NH3 Gas Sensor

    47520140

    These sensors are typically 8-pin electronic control units designed for FPT Tier 4B / Stage IV emissions systems. Ensure you match the specific cable length (e.g., 700mm vs 1000mm) required for your exact machine model.

  • NH3 Sensor / Ammonia Sensor / Aftertreatment Outlet NH3 Gas Sensor

    47520142

    These sensors are typically 8-pin electronic control units designed for FPT Tier 4B / Stage IV emissions systems. Ensure you match the specific cable length (e.g., 700mm vs 1000mm) required for your exact machine model.

  • NH3 Sensor / Ammonia Sensor / Aftertreatment Outlet NH3 Gas Sensor

    51515739

    These sensors are typically 8-pin electronic control units designed for FPT Tier 4B / Stage IV emissions systems. Ensure you match the specific cable length (e.g., 700mm vs 1000mm) required for your exact machine model.

  • NH3 Sensor / Ammonia Sensor / Aftertreatment Outlet NH3 Gas Sensor

    84382712

    These sensors are typically 8-pin electronic control units designed for FPT Tier 4B / Stage IV emissions systems. Ensure you match the specific cable length (e.g., 700mm vs 1000mm) required for your exact machine model.

  • NH3 Sensor / Ammonia Sensor / Aftertreatment Outlet NH3 Gas Sensor

    5802392179

    These sensors are typically 8-pin electronic control units designed for FPT Tier 4B / Stage IV emissions systems. Ensure you match the specific cable length (e.g., 700mm vs 1000mm) required for your exact machine model.

  • NH3 Sensor / Ammonia Sensor / Aftertreatment Outlet NH3 Gas Sensor

    5802392186

    These sensors are typically 8-pin electronic control units designed for FPT Tier 4B / Stage IV emissions systems. Ensure you match the specific cable length (e.g., 700mm vs 1000mm) required for your exact machine model.

  • NH3 Sensor / Ammonia Sensor / Aftertreatment Outlet NH3 Gas Sensor

    5802392190

    These sensors are typically 8-pin electronic control units designed for FPT Tier 4B / Stage IV emissions systems. Ensure you match the specific cable length (e.g., 700mm vs 1000mm) required for your exact machine model.

  • NH3 Sensor / Ammonia Sensor / Aftertreatment Outlet NH3 Gas Sensor

    5801627706

    These sensors are typically 8-pin electronic control units designed for FPT Tier 4B / Stage IV emissions systems. Ensure you match the specific cable length (e.g., 700mm vs 1000mm) required for your exact machine model.

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