4.2.197. SPN 520208, FMI 31, Rail PRV recognised as OPENΒΆ

Description

The rail pressure exceeds the safe operating range and the PRV is opened. The pressure will drop after the PRV is opened, and the EEM4 system recognizes the pressure variation in the rail. The PRV stays open as long as the engine is running.

Possible reasons are:

  • PRV is defective
  • The fuel system is clogged.
  • high pressure pump is defective
  • The rail pressure sensor wiring is defective
  • The rail pressure sensor power supply is not correct
  • The rail pressure sensor is defective
  • The control unit is defective

Reaction in EEM

The FC is stored and the warning lamp is activated. Engine power is heavily reduced (Degradation Level 3). The CAN message indicates active fault. The engine functions dependent on the rail pressure are not active.

Solution

First save the error log and then erase it. Restart the ECU after erasing the error log. If the fault occurs again during the next driving cycle, check the following paths:

  • Check the operation with another PRV to see if the PRV is defective.
  • Check the high pressure pump operation.
  • Check the fuel system for a possible clog (the fuel rail and the fuel lines).
  • Check the rail pressure sensor wiring, the connectors and the contact surfaces of the connector pins (possible oxidation).
  • Check the 5 V power supply to the sensor.
  • Check the operation with another rail pressure sensor to see if the sensor is defective.

NOTE: The fuel rail component removal, inspection and replacement should be performed only by qualified injection system service personnel. Special instructions may apply.

  • Check the ECU operation with another EEM4 controller. If the system is functional and the fault is not active with the replacement ECU, then the original ECU is defective.