4.2.121. SPN 4090, FMI 16, SCR system malfunction: NOx emission too highΒΆ

Description

EEM4 monitoring system has detected SCR system malfunction. NOx emission is above allowed level.

Possible causes are:

  • The SCR system is unable to dose
  • The DEF dosing module is defective or blocked
  • The used reducing agent (DEF/AdBlue) is contaminated.
  • The SCR catalyst 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:

  • Check the used reducing agent (DEF/AdBlue) quality. If any suspicions of bad reducing agent being used, the tank needs to be emptied, flushed and refilled with valid reducing agent.
  • Check the DEF system operation. Make sure SCR system is able to dose DEF/adblue.
  • Check the operation with another DEF dosing module to see if the dosing module is defective.
  • Check the SCR catalyst condition. Remove the dosing valve and look inside the catalyst. Try to see the possible DEF/AdBlue deposit problem or blockage.