“As Is” means there is no warranty or legal obligation for the seller to pay for any repairs. "As Is" sales are those where the seller has no duty to fix anything that goes wrong. What can be done about your purchase of an older car with no warranty coverage on a system that now needs an expensive fix? Without any warranty coverage there is very little, legally, you can do to force the seller to fix or pay for the repair because you bought it without any promise (warranty) from the dealer that if this part failed w/in a certain period of time, or mileage, he would repair it.
However, if during the negotiations, there was a lie about something factual, as opposed to an opinion - e.g. "Never wreck damage, no accidents, never been repossessed" - These are factual statement which, if untrue, would give you a right to cancel the contract for fraud and return the car, or keep it and get you damages which are the difference between what you paid for it and what it was actually worth as a wrecked car, and maybe legal fees. However, statements like "No accidents or wrecks to the best of my knowledge", or "It’s a good car", or similar words are considered typical dealer talk , or "puffing", or an opinion, which we all expect when we buy a car, and is not actionable. If the dealer knew it was damaged or wrecked, and lied about it, then it’s a case for punitive damages on top of any damages you suffered for buying a car not worth what you paid for it (called “diminished value”), and you can get legal fees as well.