Why does my 1995 toyota 4runner shake and have the engine light turn on when im driving on the freeway

Check tires, tread etc.

Why would that turn my check engine light on?

If it's not the tires, it could be an alignment or balance issue. The check engine light could be a multiple of things. Oil, power steering etc. First thing is first with a issue like this, check your tires first. Then alignment and balance. Does the car pull to a specific direction while driving? ( left or right? )

I just had my alignment and all tgat done. The shaking only atarts when the check engine light turns on.