Case IH 19735 – Engine Control Module (ECM) / Engine Control Unit (ECU): Maximum negative rail pressure deviation with closed pressure control valve exceeded (second stage)

The engine's Common Rail fuel system is failing to build or maintain adequate high-pressure fuel. The Engine Control Module (ECM) is detecting that the actual fuel rail pressure is significantly lower than the target pressure (a "negative deviation"). Even though the ECM has commanded the Pressure Control Valve (PCV) / Fuel Metering Unit to close completely in an attempt to force pressure to build, the pressure remains critically low.

• Tier 4b
• Farmall 90C
• Farmall 95A
• Farmall 100C
• Farmall 105A
• Farmall 110C
• Farmall 110U
• Farmall 115A
• Farmall 120C
• Farmall 120U
• Maxxum 110
• Maxxum 115
• Magnum 245
• Magnum 275
• Magnum 305
• Magnum 335
• Steiger 280
• Steiger 330
• Steiger 335
• Case Wheel Loader 621E
• Case Wheel Loader 621F
• Case Wheel Loader 621G
• Case Wheel Loader 721E
• Case Wheel Loader 721F
• Case Wheel Loader 721G

1. 1

   Inspect the pre-supply (lift) fuel pump for loose electrical connections and verify it is delivering adequate low-pressure fuel to the high-pressure pump.

2. 2

   Check the injector overflow (return flow). Excessive return flow indicates fuel is bypassing the injectors, preventing the rail from building pressure.

3. 3

   Check if the Pressure Control Valve is stuck in the open position, if the zero-delivery throttle is clogged, or if the unit has lost power due to an electrical/wiring error.

4. 4

   Verify the Rail Pressure Sensor is not outputting an implausible raw voltage signal.

1. 1

   Address the Pre-Supply Pump

   If the pre-supply pump is failing or has loose connections, repair the wiring or replace the pump. Clear the error codes and verify if the target rail pressure is reached.

2. 2

   Replace Leaking Injectors

   If the injector overflow test shows flow is out of range, the injectors are malfunctioning. Replace the faulty injectors, clear the error codes, and verify.

3. 3

   Replace the PCV and Rail

   If the injectors and low-pressure system are fine, the Pressure Control Valve is likely leaking internally. The standard repair procedure dictates changing the fuel rail along with the PCV and the rail pressure sensor. Clear the error codes and verify.

4. 4

   Replace the High-Pressure Pump

   If all previous steps fail to resolve the negative pressure deviation, the high-pressure fuel pump (HPP) is mechanically worn out and cannot generate target pressure. Replace the HPP with a new unit, clear the error codes, and verify.