3.2.257. SPN 5026, FMI 2, Upstream NOx sensor value offset check errorΒΆ

Description

The upstream NOx sensor value offset check error has been detected during the fuel cut off phase.

Possible causes are:

  • The upstream NOx sensor 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 the operation with another NOx sensor to see if the upstream NOx sensor is defective.