2.2.55. SPN 157, FMI 0, Rail pressure monitoring: Pressure above normal.ΒΆ

Description

The measured rail pressure is over the critical limit. The measured pressure is >2125bar. In case of a PCV mechanical failure, the EEM4 system continuously monitors the rail pressure, and if the measured pressure is > 2125bar, the engine will shutdown immediately.

Possible causes are:

  • The high pressure pump wiring is defective.
  • The high pressure pump is not working correctly.
  • The rail pressure sensor wiring is defective.
  • The rail pressure sensor power supply is not correct.
  • The rail pressure sensor is defective.
  • Pressure control valve (PCV) is not working correctly.

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 an active fault. The engine functions dependent on the rail pressure are not active.

NOTE: Due to the very high injection pressure (1800 - 2000 bar), there is a serious risk for injury during engine running, if the high pressure side has a leakage.

Solution

First save the error log and then do the procedure that follows:

  • Examine the high pressure pump: Look for possible high pressure pump faults and inspect them accordingly (e.g. faults with the wiring and the connectors).
  • Test the high pressure pump operation with the Service Tool test function, or have the pump inspected by an authorized Bosch service dealer.
  • In case of a damaged pressure control valve (PCV), high pressure pump or a wiring harness, replace the damaged parts according the instructions in the service manual.
  • Examine the rail pressure sensor wiring, the connectors and the contact surfaces of the connector pins (possible oxidation).
  • Make sure that the 5 V power supply to the rail pressure sensor is correct.
  • Try the operation with another rail pressure sensor to see if the sensor is defective.

NOTE: The high pressure part removal, inspection and replacement should be performed only by qualified injection system service personnel. Special instructions may apply.

See Rail pressure sensor for reference.