P0040 - OBD II Trouble Code

Our automotive experts have put together the following information about the P0040 diagnostic trouble code. We've provided the common symptoms that occur when this code is set along with the frequent repairs that address the issues related to the P0040 code.

OBD II Fault Code

  • OBD II P0040

    Fault Code Definition

    • O2 Sensor Signals Swapped Bank 1 Sensor 1/Bank 2 Sensor 1

    What does this mean? The Oxygen Sensors tell the engine control module (PCM) the amount of oxygen left over after the combustion process. each bank (or side) of the motor has its own oxygen sensor. If PCM determines that the wiring harnesses from the sensors have been crossed using a logic based strategy, the PCM will set code P0040.


    • Decreased engine performance
    • Increased fuel consumption

    Common Problems That Trigger the P0040 Code

    • Oxygen sensor wiring has been misrouted

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