Oxygen sensor failed at 68,000 miles, should not be a big deal, just remove and replace it. Wrong! Dealer says sensor cannot be replaced without a new exhaust manifold, estimate $1700.00. Toyota knows that this is a common problem and has issued a service bulletin indicating the manifold must be replaced. This problem should be covered under warranty or recall. I finally found an independent garage that was able to replace the sensor without changing the exhaust manifold.