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It is possible that a check engine light on a Toyota Highlander will come on if the coolant level is low. Usually, though, there is another light that will come on that says 'low coolant' on some older Toyota's.
Check your brake (stop) light fuse
Have vehicle scanned to determine the problem - usually in the emission control system,
Have vehicle scanned to determine the problem - usually in the emission control system,
start with engine off. press and hold that speedometer resetter while starting engine, check engine light will flash a few times then disappear.
o2 censor
I have a 2003 Highlander. Whenever I get the oil changed, the check engine light comes on within a couple of days. I finally figured out that there is a hose under the air filter case that gets disconnected when the filter is checked. Just reattach the hose and the light will reset after a few restarts of the engine.
Go call the Toyota car company or headquarters and ask the people who made the car.
To reset a check engine light for a Highlander 2003, disconnect the battery for 10 minutes. After this time, reconnect the cables.
check the gas cap... usually if you "lost" yours and/or it isn't tight this could cause the check engine light to come on
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.
For the Highlander 4 cylinders, it is on the Alternator side. To replace it, you have to take the alternator out and unscrew two bolds . Unless the engine is rebuilt, thermostat only replaced, most likely, when you rebuild the engine. check cooling tank and water hose leak first.