P0146 - OBD-II Trouble Code

Oxygen Sensor Circuit No Activity (Bank 1, Sensor 3)

Our emissions expert has put together the following information about the P0146 fault code. We have also included diagnostic procedures you can take to your repair shop if the mechanic is having difficulty analyzing the code.

OBD II Fault Code

  • OBD II P0146

Fault Code Definition
The Rear Catalyst Monitoring Oxygen Sensor evaluates the rear most Catalytic Converter's emissions-reducing capability in a system with two Catalytic Converters for each bank of cylinders. P0146 is set when the Rear Oxygen Sensor signal does not show enough activity to indicate fuel control and closed loop fuel management


  • Check Engine Light will illuminate
  • In many cases, no abnormal symptoms may be noticed
  • In some cases, the vehicle will fail an Emissions Test
  • In many cases, the NOx emissions will be elevated

Common Problems That Trigger the P0146 Code

  • Defective Rear Most Oxygen Sensor 
  • Faulty Rear Most Oxygen Sensor wiring or connections

Common Misdiagnoses

  • Oxygen Sensor is replaced when the problem is faulty sensor wiring or connections
  • Rear Catalytic Converter or Rear Oxygen Sensor is replaced when the problem is an exhaust leak before the Rear Oxygen Sensor