I was on vacation and drove in the rain for ten hours and then the vsc light and check engine light came on. both stayed on for six days then went off on sunday. Why or what would make it come on. It also did this last January but went off on the same day.
When the VSC light comes on the check engine light comes on every time. The problem is most likely with the VSC computer.
Two things to check. First, the brains for this is under the front passenger seat. It's common for one of the harnesses to come undone by someone shoving something under that seat or whatnot. Maybe you have a loose one and the problem is exacerbated by humidity. Second, each wheel has a sensor and it's not uncommon for them to come loose from the hub. I would pull all four wheels and just make a visual inspection of each. There are two lines going to each hub, a fat brake line and a skinny wire. You want the wire. Just make sure they're not loose, and if they are tighten them back down. It's easier done than said.... it will be obvious if there is a problem.
Just get a code reader the next time it happens and see what the code is. The check engine light doesn't come on because the VSC light comes on. It's the other way around. The check engine light comes on because something might be amiss in anything having to do with the overall emissions control system (O2 sensors, evap system, ignition coils, catalysts, etc). Because the engine might not run properly, the VSC disables itself because there's some situations where VSC can trigger on an abnormally running engine and cause the engine to stall. Not good, and also potentially dangerous. So VSC disables itself until the CEL clears or the problem goes away. The fact that it comes and goes means you have some sort of marginal or erratic emissions issue. Best to just get a code reader and see what it is/was. Even if the light goes out, sometimes the code will linger in the "pending" code section for awhile.
The cel code will be stored until it is cleared by a scanner or the battery is disconnected. If it is emissions related it is likely an 02 sensor. As good as the Toyota`s are, their 02 sensors seem to die quickly. I agree with steVTEC and just have the vehicle scanned for codes to give you some piece of mind.