I checked around today to see if any of the auto parts stores but Auto Zone did free vehicle computer or check engine light diagnostic.  It is a one to two minute test, so it is hard to understand why they wouldn't.  Napa no, Advance Auto no, only AZ did it.  Free battery tests are more common, maybe because they are more likely to make money on the test?

All the Advance Autos around me read check engine lights for free.  I'm sure it varies by location.

 

A few years ago I bought a cheap code reader from fleabay (about $20).  It does the job fine.

O'Reilly auto parts does the tests for free, only they won't reset (turn off) the light.

 

Just my 2 bucks

Do you have an android phone? If so, Look into the Torque App. The App is free, you just need a Bluetooth OBD2 adapter. Like $15 on eBay.

 

There are also plenty of inexpensive code readers out there. Very useful if you're stuck in the driveway and can't get to a a parts store to has them read the code. And after a few uses they usually pay for themselves in fuel savings.

When you say it can pay for itself in fuel savings, what does it do to save fuel. I am very interested in one of these for my 1999 outback... Thanks

setting aside the help you might get repairing your car, i think he means, less driving to a parts store that will read a code. That is, you get a code, you walk into your own house to get a reader instead of driving 2 miles to VatoZone and back.

California, I'm told, has some asinine law law that prohibits the parts stores from doing their free checks. Auto Zone employee apologetically informed me. As a company the do it free everywhere else. shops here want to charge $40-$100 to do it.

 

I bought a scanner from harbor freight with a 20% off coupon and have happily offered to scan free for friends and family in the area.

As cheap as scanners are anymore anyone who does their own work on their vehicles should purchase one. 

 

The nice thing is that they are not usually vehicle specific and can be used on all models.