Incorrect Oxygen Sensor on 2.4L Engine

An engine stumble or stall after startup on some 2010-2017 Equinox and Terrain models equipped with the 2.4L 4-cylinder engine (RPO LAF, LEA) may be caused by a faulty aftermarket or incorrect upstream oxygen sensor (HO2S). In most cases, no DTCs will be set.

If an engine stumble or stall condition after a hot or cold start is found, monitor the upstream oxygen sensor voltage. The condition may occur more often when the vehicle is shifted into gear. The voltage may be skewing high, staying at 800mv or higher, which causes the ECM to believe the engine is running rich and results in an unnecessary lean out of the fuel system.

Check if the condition does not occur with the upstream oxygen sensor disconnected, which may confirm that the oxygen sensor is the issue. Do not remove the pigtail from the sensor. (Fig. 17) Inspect the faulty oxygen sensor to determine if it is an aftermarket part or is the incorrect oxygen sensor, such as a sensor for a different vehicle application or position.

Fig. 17

Be sure to handle the oxygen sensor carefully. The external clean air reference is obtained by way of the oxygen sensor signal and heater wires. Any damage to the wires, connectors, or terminals could result in the obstruction of the air reference and degraded sensor performance.

TIP: A special anti-seize compound is used in the HO2S threads. The compound consists of liquid graphite and glass beads. The graphite tends to burn away, but the glass beads remain, making the sensor easier to remove. New or service replacement sensors already have the compound applied to the threads. If the sensor is removed from an exhaust component and, if for any reason, the sensor is to be reinstalled, the threads must have anti-seize compound applied before reinstallation.

GM Engineering is currently evaluating this condition and working on a repair recommendation. For additional information, refer to #PIP5624.

 

– Thanks to Tim Lightfoot

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