One problem related to engine clicking and tapping noises has been reported for the 2003 Toyota Highlander. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2003 Toyota Highlander based on all problems reported for the 2003 Highlander.
My 2003 Highlander limited 6-cyl. 4wd vehicle has a loud audible clicking noise (sounds like valve lifters ticking) eminating from the engine since I purchased the vehicle new from page Toyota in Jan '2003. The clicking noise is only present when the engine is running. The clicking noise is always audible but the volume decreases as the vehicle reaches normal operating temperature. The clicking noise is very loud when the vehicle is cold. The clicking noise frequency increases with increasing engine rpm and decreases with decreasing engine rpm. The Toyota red holman customer service representative stated that the clicking noise is normal and can not be reduced or eliminated.