The Check Engine Light may illuminate because a component of the oxygen sensor stops working. As a result the engine computer is unable to determine the proper ratio of air to fuel for the engine. Replacing the failed oxygen sensor should correct this concern.Google+
Car Problem Reports
Toyota Highlander Check Engine Light Due to Failed Oxygen Sensor Component
Toyota Highlander Problem
Average Mileage: 88,714 mi (50,000 mi - 135,000 mi)
Visitor, 2002 Toyota Highlander, 89,000 mi
when humid or rainy it misses I put it on a diagnoses at auto zone they reported it to be the oxygen sencor #2
The CE light was on and my gas mileage was awful. I got the part replaced. The CE light turned off, but my gas mileage only improved a little.
I had two of these go and the mechanic said they are common on Highlanders.
Visitor, 2001 Toyota Highlander, 117,000 mi
Have literally taken this in to be dealt with 4 times without resolution. Check engine and VSC still come on until we started ignoring it.