Case IH 1080.03 - ACML – Engine Control Unit (ECU): Fuel Rail Pressure Sensor Supply Voltage High

The Engine Control Unit (ECU) has detected a voltage above the normal specification on the ECU's 5-volt sensor supply circuit (5V Reference Voltage 2). Specifically, the supply connection to the fuel rail pressure sensor is shorted to a high voltage source.

• VESTRUM CVX
• Case IH Steiger Series (350, 400, 450, 500, 550, 600 horsepower models)
• Case IH Puma Series (140 to 225 models)
• Case IH Maxxum and Farmall Series
• Case IH Vestrum Series
• Case IH Combines (e.g., 2188, 2388, and legacy models)

1. 1

   Test the voltage directly at the Engine ECU, specifically checking ECU Pin R3 (5V supply) and Pin P3 (Return/Ground).

2. 2

   Use a multimeter to verify if the 5V reference circuit is reading out of range high (e.g., above 4.5V - 5.5V depending on the specific sensor threshold).

3. 3

   Trace the wiring harness from the Engine ECU to the Fuel Rail Pressure Sensor to look for rubbed, chafed, or melted wires that could be shorting the 5V line to a 12V power source.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the battery to prevent further electrical damage.

2. 2

   Isolate the Short

   Disconnect the Fuel Rail Pressure Sensor. Reconnect the battery and turn the key to the ON position. Measure the voltage at the harness connector. If the voltage is still too high, the short to power is in the wiring harness. If the voltage returns to a normal 5V, the sensor itself has failed internally and is shorting the circuit.

3. 3

   Repair Wiring

   If the harness is shorted, locate the damaged section of the wire between the ECU (Pin R3) and the sensor. Splice and heat-shrink the damaged wire, or replace the affected harness section.

4. 4

   Replace Sensor

   If the sensor is the source of the short, remove and replace the Fuel Rail Pressure Sensor.

5. 5

   Clear Codes

   Reconnect all components, turn the machine on, and use the diagnostic interface (via the Armrest Control Module / AFS monitor) to clear the fault codes.