Check-engine light on 2008 Toyota Sequoia

The check-engine light keeps coming on (4th time). Each time I take it to the Toyota dealer, they tell me that it was the gas cap (vapor lock)? How can this be prevented?

Asked by for the 2008 Toyota Sequoia
Your car is too new to have this repeated problem and them not to be able to fix it. Perhaps you are not adequately tightening the gas cap after refilling but if you are they need to properly test the evaporative emission control system. Either try another dealer or contact Toyota North America and voice your disappointment at having your car brought in 4 times for the same problem.