4.2.273. SPN 521008, FMI 0, SCR system ERROR: DEF pressure reduction failure

Description

The EEM4 monitoring system has detected an SCR system ERROR. SCR system can’t perform pressure reduction.

Possible causes are:

  • The DEF supply module inlet connector is blocked
  • the DEF inlet line hose is defective
  • The DEF supply module main filter is defective
  • The used reducing agent (DEF/AdBlue) is 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:

  • Change the DEF supply module main filter.
  • Change the DEF supply module inlet connector.
  • Check the DEF inlet line hose by visually to detect any mechanical falure eg. hose is flattened.
  • Remove the DEF inlet line hose to detect blockage in the hose.
  • 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.