Another reason kids can't act as shade tree mechanics like in years past is because engines have become so much more complex. It used to be you could work on an auto engine with a basic toolbox. Not anymore. People take their cars to the repair shops because they know they can't do the work themselves.
My experience is, sometimes yes, sometimes no.
Those computers can also help you quickly diagnose a problem. I've got a 1999 Ford. The "Check Engine" light came on at 150,000 miles. I took it by Auto Zone, they hooked up a handheld computer and downloaded the codes - for free. I changed out two oxygen sensors and the light went away. Total cost $90 and an hour of work....