4.2.129. SPN 4332, FMI 14, SCR system ERROR: Pressure drop test failure

Description

The EEM4 monitoring system has detected an SCR system ERROR. Pressure didn’t drop when dosing valve was opened during pressure check in detection mode.

Possible causes are:

  • The DEF pressure line is defective (Possible blockage or mechanically defective)
  • The DEF dosing valve is blocked
  • The DEF supply module main filter is defective
  • The used reducing agent has been contaminated
  • The DEF supply module is defective.

Reaction in EEM

The FC is stored and the warning lamp is activated. The CAN message indicates active fault.

NOTE: The present fault is classified as an emission related fault. Engine power will be reduced after a certain time defined by an authority.

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:

  • Remove the DEF dosing valve and check the nozzle of the dosing valve to see the possible blockage.
  • Check the pressure line visually to detect any mechanical failure eg. if the hose is flattened.
  • If the vehicle was started in cold conditions and the SCR system was frosted, there could be ice in the pressure line.
  • Change the DEF supply module main filter.
  • Change the DEF supply module backflow connector.
  • Check the used reducing agent (DEF/AdBlue) for contamination and change it, if necessary.
  • Check the operation with another DEF supply module to see if the supply module is defective.