If you go to Toyota USA's FAQ site,
http://www.toyota.com/help/faq.html , and search for "timing" you will get this page titled "Timing Belt and Timing Chain":
http://toyota.custhelp.com/cgi-bin/t...i=&p_topview=1 , it depends on whether you have the 4-cylinder engine (you'd have a timing chain) or the V6 (6-cylinder) engine (you'd have a timing belt) in your 2003 US Toyota Highlander.
According to the "Timing Belt Recommendations" page,
http://toyota.custhelp.com/cgi-bin/t...GltaW5n&p_li=# , the timing belt should be replaced every 90,000 miles OR 6 years, whichever occurs first. There is no prescribed replacement interval for a timing chain.
You can also view your scheduled maintenance guide (usually called the "Passport to Performance") for your vehicle at
http://smg.toyotapartsandservice.com/ to see what other maintenance items (besides the timing belt) should have been performed and at what intervals.
When should I replace the timing belt on an 03 Highlander?
Linear Mode
