theres a few things that can set this code, but the most common is a thermostat thats stuck open and not letting the engine warm up fast enough. to check it, take it out and look at it. at room temp it should be closed all the way. if its open, even partialy, replace it. in fact, even if it looks ok u may wanna replace it anyways. its a cheap part, and some times a thermostat thats starting to fail can stick intermittantly, so even if it looks ok when u look at it, it could act up some times when its in the engine.