From what I understand, they don't pay for diagnostic work. If you come into the shop with a rod knocking and no oil pressure, any competent mechanic would say you need a new engine. Car Shield requires that the engine be torn down to verify where the problem is before they will pay. So, they may pay for a new engine but you are still on the hook for all of that diagnostic work of tearing down the engine to find exactly where the problem is. This info was on a news program talking about class action lawsuits against Car Shield.