Q: Can a p015b be caused by a loose gas cap?

Trouble code P015b is not related to, or potentially caused, by a loose gas cap or any other EVAP system malfunctions for that matter. The code instead relates to degraded performance of one of the engine’s oxygen sensors. In some models of Cruze there is a PCM software update that is relevant to this specific code and there is also a possibility that the sensor on this vehicle is subject to premature contamination. In any event, the code implicates possible degradation in engine efficiency and performance and thus obviously the underlying fault should be fully resolved before buying the car or, in lieu of that, be sure to request an adequate discount to cover any necessary diagnostic and repairs. If you want YourMechanic to diagnose and repair the fault, the recommended service to request is a check engine light diagnostic.

You can protect yourself in a used car transaction by requesting a pre-purchase vehicle inspection. That inspection, carried out by a certified Mechanic, dispatched to your location, will give you the data that you need to make a fully informed, intelligent decision and minimize your risk in buying a used car. If you look at the just cited link for YourMechanic’s inspection service, you will see a long list of the vehicle systems that must be inspected as well as details of YourMechanic’s inspection methodology. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.