I imagine that the check engine light is on which means the engine codes need to be read to find out what is wrong. Being in limp mode means there is a serious problem that needs to be addressed.
Limp mode is your cars way of saying "I'm not going to let you go faster because I think there is something wrong with the engine/transmission. In my experience, getting the code cleared fixes the problem temperately. The code your computer reads must be looked at by a mechanic to understand its meaning.
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