I wasn't even out of Power Wheels in the hey day of the Knight Rider series, but a number of episodes stuck out to me. One I vaguely remember was when K.I.T.T. was somehow turned rogue, and Michael had to climb through the roof as the car was moving, and insert a computer circuit board of some kind to bring his friend back.
What episode was this, and in what season?.
This is Killer K.I.T.T. (Season 4, Episode 13).
Marco Berio, a former employee of F.L.A.G, uses his knowledge of K.I.T.T. to override the Trans Am's CPU and turn him against his owner, Michael Knight.
At the end of the episode Michael jumps onto K.I.T.T. and climbs in through the sun roof to insert a chip to fix him.
I was wrong with my previous comment and deleted it. Now I think I have the correct answer.
Looks like there are four episodes that deal with reprogramming K.I.T.T. somehow, one per season:
Of these, only "Chariot of Gold" and "Killer K.I.T.T." show K.I.T.T. who turned evil, so it must be one of these two.
Anyhow, here are the teasers of the episodes so you can check:
