Some customers of 2010–2017 Chevrolet Equinox or GMC Terrain models equipped with the 2.4L (LAF or LEA) powerplant may cite a concern with the engine stumbling or stalling after start-up, whether the engine is hot or cold. There are typically no related DTCs and the issue may be more noticeable when the vehicle is placed into gear.


The condition may be caused by a faulty aftermarket or incorrect upstream oxygen sensor (HO2S).

To correct the problem:

  • Monitor the upstream oxygen sensor voltage when the condition is present. The voltage may be skewing high (staying at 800mv or more), causing the ECM to believe that the engine is running rich, resulting in an unnecessary lean out of the fuel system.

  • If the condition ceases when the sensor is disconnected, this may confirm the sensor as the source of the problem and that a faulty or incorrect one was used.

  • To resolve the concern, ensure that the proper sensor is installed for the engine application.