2.2.336. SPN 520388, FMI 31, Rail Pressure control: Over pressure protection mode activated.ΒΆ

Description

The maximum number of overpressure reaction activations has been reached. Activating reactions to bring the pressure back down to the acceptable range.

Possible causes are:

  • The pressure control valve is not working correctly (stuck).
  • The pressure control valve wiring is defective.
  • The high pressure pump is not working correctly.
  • The high pressure pump wiring 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 pressure before the high pressure pump is too high (e.g. in the case of an electric presupply pump with a pressure relief valve).

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 (> 2000bar), there is a serious risk for injury during engine running , if the high pressure side has a leakage.

NOTE: Over pressure protection mode activation needs to be cleared with an official service tool.

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.
  • Examine the pressure control valve: Look for possible valve stucks and inspect them accordingly (e.g. faults with the wiring and the connectors).
  • Examine the electric presupply pump: Look for possible relief valve stucks and inspect them accordingly (e.g. faults with the wiring and the connectors).
  • In case of a damaged pressure control valve (PCV), high pressure pump or a wiring harness, replace the damaged parts according to 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.