Two stories, two cars, both recent. 2014 Equinox with less than 7K on it. On a Friday, two days before leaving on a 1400 mile trip home the MIL light comes on and stays on. I drive it to the dealer and in the write-up bay they hook a scan tool up and an O2 sensor has not responded quickly enough to make the computer happy. They are booked, can't get it in and we both agree that it is not serious enough to worry about anyway as there is also no noticeable difference in the way the car runs or operates. Next day upon starting light is not on and was not on all the way home and a month later has not come on again.
2012 Regal has Service Brake Assist, Service Traction Control and Service Power Steering message in DIC within about 4 four months of getting the car. It is affecting the power steering making steering effort slightly heavier but also, wheel does not return to center after turning without some assistance. I take it in and they have it for over a week. They are contacting the geniuses and they ultimately do some reprogramming and declare it fixed. Several weeks after picking it up, the messages and the symptoms return. It "heals" itself within a day or so and I drive the car for another 19 months and never have the situation repeat itself. Last week, it happens again but it only lasted for a day. No problem at the moment. It's a lease and goes back at the end of the month and they can deal with it at that time. It still has a lot of warranty left.
Intermittent's are a bitch.