Timing belt or chain

2003 toyota highlander 3.0 v-6 (awd) - Does it have a timing belt or chain and how often does it need to be replaced?

www.gates.com (a belt and hose maker) shows timing (cam) belt part #257. So, yes, it has a timing belt which is due time/mileage change as shown in your Owner’s Handbook, or the maintenance manual.

As with most other important issues with your vehicle, the answer is sitting in your glove compartment. Look for the Toyota Maintenance Schedule, which is contained either in the Owner’s Manual, or in a separate booklet with an appropriate title.

Now, take a look at the maintenance procedures that are listed for mileage intervals such as 90,000 miles, 100,000 miles, 105,000 miles, and 110,000 miles. If you have a timing belt, the replacement of it will be listed for one of those mileage intervals. Also, note that each mileage interval also has an alternative elapsed time interval, such as “90,000 miles or 6 years, whichever comes first”, or “105,000 miles or 7 years, whichever comes first”. Since rubber parts like a timing belt deteriorate over time, even if an engine is never started, the elapsed time factor is just as important as the odometer mileage factor.

If you have a timing chain, replacement will not be listed as a maintenance procedure, as this component lasts for a very long time in normal service and most vehicles never need to have the timing chain replaced.

All of this being said, since it appears that you have never utilized the maintenance schedule for this vehicle, I would strongly suggest that you compare your service invoices (You DO save them, I assume) with the maintenance schedule in order to verify that you are up to date (in terms of both mileage and elapsed time) with the procedures that are listed. Even if you don’t have a timing belt that needs to be changed, failure to perform other listed maintenance procedures could also doom your vehicle to an early demise.