Case IH 19743 – Engine Control Module (ECM): Fuel Metering Unit: Maximum positive deviation of rail pressure exceeded.

The Engine Control Module has detected that the actual fuel pressure in the common rail is significantly higher than the commanded (target) pressure setpoint. A positive deviation indicates an over-pressurization condition where the fuel metering unit is unable to reduce or regulate the fuel flow entering the high-pressure pump, or the pressure relief valve is failing to vent the excess pressure.

• Tier 4b
• Magnum
• Maxxum
• Puma
• Steiger
• SR220
• SR250
• SV250
• SV300
• TR320
• TV380

1. 1

   Connect the CNH Electronic Service Tool (EST) and monitor the 'Actual' vs. 'Desired' fuel rail pressure

2. 2

   Perform a Key-On, Engine-Off (KOEO) test to check the rail pressure sensor reading (should read zero or atmospheric pressure)

3. 3

   Inspect the wiring harness and connectors going to the Fuel Metering Unit (FCA/M-PROP) and Fuel Rail Pressure Sensor for shorts or damaged pins

4. 4

   Check if the Fuel Control Actuator (FCA) is mechanically stuck, as it defaults to maximum fuel pressure if it loses electrical connection

5. 5

   Verify if the mechanical pressure relief valve (PRV) on the fuel rail has been forced open or is leaking

1. 1

   Relieve System Pressure

   Ensure the engine is off and the high-pressure fuel system has completely depressurized before opening any lines. Warning: High-pressure fuel spray can cause severe injury.

2. 2

   Inspect/Replace the Fuel Rail Pressure Sensor

   If the KOEO diagnostic check showed skewed voltage/pressure readings, replace the fuel rail pressure sensor located on the fuel rail and torque to OEM spec.

3. 3

   Replace the Fuel Metering Unit (FCA / M-PROP)

   If the sensor is reading accurately but the pump is over-pressurizing the rail, the metering unit is mechanically stuck. Locate the FCA on the back of the Bosch CP3/CP4 high-pressure fuel pump. Disconnect the electrical harness. Remove the mounting screws (usually 3 Torx-head screws). Pull the FCA straight out (some wiggling may be required to unseat the O-rings). Lubricate the O-rings on the new FCA with clean diesel fuel and press it into the pump housing. Install and tighten the screws, then reconnect the harness.

4. 4

   Bleed the System

   Prime the low-pressure fuel system to remove any introduced air.

5. 5

   Clear Codes and Test

   Use the diagnostic tool to clear code 19743 (and any related 3293/3309 codes). Start the engine and verify that the actual rail pressure closely tracks the desired rail pressure across the RPM range.