2015 4runner trac off and check engine

When I started my 2015 4runner this morning, the check
engine light came on along the the trac off light. Also, the
car is sputtering. I bought a new gas cap and installed it
after reading in the forum, but it not help. A scan showed a
code for a misfire in the third cylinder. I changed the plug in
that cylinder, but it did not help. I plan to change out the
other plugs as well. The forum suggested a bad or dirty
speed sensor.  Would the speed sensor or gas cap cause
the misfire? Am I looking at more than one problem?
Something else to look for? Thanks for any help