Riding highway do not require experience, you are riding in a straight line at a constant speed with no shifting and hard braking (hopefully); it doesn’t get any easier than that.
Why would the check engine light turned on when cruising at 4k?? NO check engine light should be on at any RPM. Are you sure it is the check engine light?
May be the guy set the shift light to turn on at 4K rpm?? :lol