Pontiac Repair: Limp Home mode

Question
I have a 2007 Pontiac G6.  Bought from a dealership and literally 20 miles it went into limp home mode.  No service engine soon light, and does not look like any thing has been disturbed around the engine.  How do I check on this with out a service engine soon light to throw off a code?

Answer
Hi pierce:

well usually when that happens a key cycle off and on will return normal operation unless what ever happened is a hard fault. did you get any messages on the radio display like reduced engine power? and service engine soon light on? if it is running normal now stop by any of the big box auto parts stores and have it scanned for codes they do this for free is what is any codes stored and you can go from there. just a question does this have a sun roof and was it raining when it happened?