I replaced The gas cap and the check engine light is still saying bad

As the repair of my Highlander can testify, that emission control section is complicated.

Squirrels dined on my tank vapor hose. That started the problem. The tank had to be replaced cause the hose was attached to it, and they replaced the cap for good measure.

Well, then they had to replace a filter in the engine area. Then they had to replace a valve in the engine area. Then they had to replace the tank pump seal - that they probably should have replace with the tank.

Bottom line - there are many things that can cause that DTC.