4.2.55. SPN 157, FMI 14, Rail pressure, Leakage detected at low idleΒΆ

Description

The EEM4 monitoring system has detected a leakage on the high pressure side of the injection system by quantity balance.

NOTE: Due to the very high injection pressure, while engine is running, there is a serious risk for injury if there is a leak on the high pressure side.

Possible causes are:

  • Air in the fuel at high pressure side(e.g. empty tank)
  • The injector is not working correctly (internal leakage)
  • The fuel side feed pipes are leaking (internal leakage)
  • The pressure relief valve is not working properly(leakage)
  • The high pressure pump is not working properly
  • MPROP solenoid valve in the high pressure pump is not working properly(defective)
  • There is a leakage at high pressure side(external leakage)
  • The rail pressure sensor wiring is defective
  • The fuel filters are full

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:

  • Stop the engine. Check the engine high pressure pipes etc. visually for a possible leakage.
  • 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.
  • Check the pressure relief valve visually for impurities. If there are impurities, clean the valve or replace it with a new one. Tighten the valve according to the instructions in the service manual.
  • Check the nozzles operation with Service Tool test function or have the injectors inspected by an authorized Bosch service dealer.
  • Check the high pressure pump operation with Service Tool test function. If test results are showing leakage at high pressure pump, defective part can be high pressure pump or MPROP solenoid valve.
  • In case of damaged injector,pressure relif valve, high pressure pipe, rail pressure sensor or wiring harness, replace the damaged parts according to the instructions in the service manual.
  • The fuel filter service. The filters are full and need to be changed.

Solution2: Valid only for 4-valve engines.

  • Check the tightness of the injector side feed pipes. The correct torque tightening and operating instructions can be found in the engine repair manual.
  • 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.

See Rail pressure sensor sensor for reference.