Case IH F-5571-31 - ECU – ECU: Maximum rail pressure exceeded

This fault code indicates that the fuel rail pressure has exceeded the maximum allowable limits of positive deviation. The system has detected that the pressure inside the high-pressure common rail is dangerously high, which usually triggers a limp-home mode (torque and RPM reduction) or engine shutoff to protect the fuel system components.

• MAGNUM AFS Connect
• Case IH Magnum AFS Connect
• Steiger AFS Connect
• Puma
• Maxxum
• Optum

1. 1

   Check the Rail Pressure Sensor (RDS) and its wiring harness for a short circuit to battery/12V or ground, which can cause erratic or incorrect voltage readings.

2. 2

   Check the Pressure Relief Valve (PRV) for tightness and opening pressure. Verify if it is defective, stuck closed, or has reached its maximum allowed opening count.

3. 3

   Check the Fuel Metering Unit (Suction Control Valve / M-PROP) and its wiring harness for a short circuit to the battery or a mechanically stuck valve.

4. 4

   Check fuel return lines for any restrictions or clogs that could cause backpressure and artificially raise rail pressure.

1. 1

   Wiring & Harness Repair

   If the diagnostic checks reveal a short circuit in the rail pressure sensor or metering unit wiring harness, repair or replace the damaged section of the harness.

2. 2

   Replace the Pressure Relief Valve (PRV)

   If the PRV is defective, leaking, or has exceeded its maximum allowed opening count (often logged alongside this code), it must be replaced.

3. 3

   Reset the PRV Counter

   After replacing the PRV, you must use an authorized Case IH diagnostic tool (EST) to reset the PRV opening counter (timer monitoring opening status) via the appropriate routine control service. If this is not reset, the ECU may continue to limit engine performance.

4. 4

   Replace the Rail Pressure Sensor

   If the sensor is proven to be short-circuited internally or is outputting erratic data despite good wiring, replace the sensor.

5. 5

   Replace the Fuel Metering Unit

   If the metering unit on the high-pressure pump is stuck open and over-pressurizing the rail, replace the unit.

6. 6

   Clear Codes and Test

   Clear the F-5571-31 code from the ECU and perform a test run under load to ensure rail pressure tracks the setpoint accurately without exceeding maximum limits.