So,recently while driving my 2015 kia optima the engine started making a rattling or knocking sound when I would accelerate. Soon after the CEL came on and I promptly took it to my dealer. The engine only has 70k miles and I've always maintained it. The dealer said this has relatively common and they will have to run test over the next 3 weeks to determine what's going on. Is this a normal time frame for diagnosing an engine problem and should it be covered under warranty. Thanks in advance for any advice.