3.2.384. SPN 521017, FMI 31, Upstream NOx sensor value stuckΒΆ

Description

The EEM4 monitoring system has detected: The upstream NOx sensor value stuck.

Possible causes are:

  • The upstream NOx sensor is defective.
  • The upstream NOx sensor is installed incorrectly.
  • The upstream NOx sensor wiring 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 which is 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 that the upstream NOx sensor is connected correctly.
  • Check the upstream NOx sensor wiring, the connectors and the contact surfaces of the connector pins (possible oxidation).
  • Check that the upstream NOx sensors is effective. Change the defective sensor to a new one.

See NOx sensor for reference.