2.2.140. SPN 3231, FMI 2, Downstream NOx sensor: O2 signal stability errorΒΆ

Description

Communication problem of the NOx sensor.

Possible causes are:

  • The NOx sensor is tampered.
  • The NOx sensor type is incorrect.
  • The NOx sensor is defective.

Reaction in EEM

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

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

Solution

First save the error log and then do the procedure that follows:

  • Check the NOx sensor wiring, the connectors and the contact surfaces of the connector pins (possible oxidation).
  • Check the NOx sensor power supply availability in connector pins.
  • Check the operation with another NOx sensor to see if the sensor is defective.

See NOx sensor for reference.