The "check engine" light is not solely dedicated to the air filter and pcv valve. There are other things that can cause this caution light to illuminate on the dashboard. Assuming you bought this car new and that it has but 37k miles on it, it's most likely still in warranty and Toyota should be fixing this problem for you.
The 2008 Toyota Highlander has a V6 engine.
The 2004 Toyota Highlander has an inline 4 engine.
The 2003 Toyota Highlander has an inline 4 engine.
The 2013 Toyota Highlander has an inline 4 engine.
The 2005 Toyota Highlander has an inline 4 engine.
The 2012 Toyota Highlander has an inline 4 engine.
The 2010 Toyota Highlander has an inline 4 engine.
The 2009 Toyota Highlander has an inline 4 engine.
The 2007 Toyota Highlander has an inline 4 engine.
The 2001 Toyota Highlander has an inline 4 engine.
The 2002 Toyota Highlander has an inline 4 engine.
The 2011 Toyota Highlander has an inline 4 engine.