Case IH 546 – Engine Control Module (ECM): Fuel Pressure sensor voltage is too high

The Engine Control Module (ECM) is receiving a signal voltage from the fuel delivery pressure sensor that exceeds the normal operating range. This is typically caused by a short circuit to a high-voltage source, an open circuit on the sensor's ground/return wire, or an internal failure of the sensor itself. When this code is active, the engine may run rough, experience a loss of power, or fail to start.

• MX Magnum
• STX Steiger
• Steiger series (375, 535)
• Magnum series
• MX/TG series
• Farmall series (95, 105, 115)
• Axial-Flow 7010
• Axial-Flow 7120
• Axial-Flow 7230
• Axial-Flow 8010
• Axial-Flow 9010

1. 1

   Inspect the Harness and Connector: Disconnect the fuel pressure sensor and inspect the connector pins for moisture, corrosion, or pushed-back pins.

2. 2

   Check ECM Supply Voltage: Using a multimeter, verify that the ECM is supplying the correct reference voltage to the sensor (typically 5.0 ± 0.2 VDC on the supply pin).

3. 3

   Check for Open Ground: Test the sensor return (ground) circuit between the sensor connector and the ECM for an open circuit.

4. 4

   Check for Shorts: Test the signal wire for a short circuit to the 5V supply or battery voltage.

5. 5

   Check for Shared 5V Codes: Verify there are no other active fault codes related to the 5V sensor supply circuit. If the 5V supply is shorted high, multiple sensors will throw high-voltage codes simultaneously.

1. 1

   Preparation

   Turn off the engine, remove the key, and disconnect the battery to prevent electrical spikes.

2. 2

   Locate the Sensor

   Locate the fuel delivery pressure sensor, which is typically threaded into the high-pressure fuel rail or the integrated fuel system module (IFSM).

3. 3

   Clean the Area

   Thoroughly clean the area around the sensor. Warning: The high-pressure fuel system is extremely sensitive to contamination. Even a single speck of dirt can cause injector failure.

4. 4

   Remove the Sensor

   Disconnect the electrical harness. Carefully unscrew and remove the faulty fuel pressure sensor.

5. 5

   Install the New Sensor

   Thread the new sensor into the fuel rail. Note: Bosch OEM fuel rail pressure sensors are designed as a "one-time torque" item. They crush to seal; removing and re-installing an old sensor can cause high-pressure fuel leaks. Torque the new sensor strictly to the OEM specification found in your specific engine's service manual.

6. 6

   Reassembly

   Reconnect the electrical harness, ensuring it clicks securely into place. Reconnect the battery.

7. 7

   Clear Codes and Test

   Turn the key to the ON position, connect a diagnostic tool, and clear the inactive fault codes. Start the engine, check for fuel leaks around the sensor base, and verify that the engine runs smoothly without throwing Code 546.