Case IH 19744 – Engine Control Unit (ECU): Maximum positive deviation of rail pressure exceeded concerning set value PCV

This code indicates an overpressure condition in the common rail fuel system. Specifically, the actual fuel rail pressure is significantly higher than the target (setpoint) pressure commanded by the engine control module. The system is attempting to regulate and lower the pressure via the Pressure Control Valve (PCV) or Fuel Metering Unit (MPROP), but the pressure remains too high.

• Tier 4b
• Magnum series (245, 275, 305, 335)
• Steiger/STX series
• Puma series
• Maxxum series
• Farmall series (90C, 110A, 120U)
• Axial-Flow series
• Case wheel loaders (621F, 721G)
• skid steers

1. 1

   Use the CNH Electronic Service Tool (EST) to monitor Actual Rail Pressure versus Target Rail Pressure at idle and under load.

2. 2

   Inspect the wiring harness, pins, and connectors at the Fuel Rail Pressure Sensor and the Pressure Control Valve (PCV) for corrosion, chafing, or loose connections that could cause false signals.

3. 3

   Check for physical restrictions, kinks, or blockages in the fuel return lines going back to the fuel tank. A blocked return line will cause pressure to spike.

4. 4

   Check for air ingress in the low-pressure fuel supply side and ensure fuel filters are not severely clogged.

1. 1

   Clear Restrictions

   If the return line flow test reveals a blockage, clear the lines or replace the pinched hoses. Retest the machine.

2. 2

   Test the Fuel Rail Pressure Sensor

   If the sensor is sending an artificially low voltage reading to the ECU, the ECU will command the PCV to increase pressure, resulting in an actual mechanical overpressure. Check the sensor's 5V reference and signal wire. If the sensor is out of specification, replace it.

3. 3

   Test/Replace the Pressure Control Valve (PCV)

   The PCV (often mounted on the high-pressure pump) can mechanically stick closed due to fuel contamination or internal wear, preventing it from bleeding off excess pressure. Remove and inspect the valve for metal shavings. If defective, replace the PCV.

4. 4

   High-Pressure Pump Replacement

   If the PCV, rail pressure sensor, and return lines are all functioning perfectly, the high-pressure fuel pump itself has suffered an internal mechanical failure and must be replaced.

5. 5

   Post-Repair

   Clear the fault codes using the CNH EST, bleed the fuel system, and test drive the machine under heavy load to ensure target and actual rail pressures match.