NHTSA Complaint #11471914 — 2019 HONDA ACCORD

I am filing this complaint because I just took in my 2019 honda accord to the honda service department so they can look at the issue with the sensor lights that are going off in my car. I thought it was a simple malfunction with the sensors but they came back telling me that there is a misfire issue with the engine causing the sensor lights to engage and all going off at the same time. My car only has 37000 miles on it and its less than 3 years old. I've taken the car to a 3rd party mechanic for regular maintenance work and its up to date on oil changes and all other maintenance that is required for the car. The Honda folks submitted for the warranty to cover the repairs of $4800 to replace the head gasket replacement along with the machining of the engine head. I have not gotten into an accident now have I used my car to race anyone that would cause the car to warp to that point. I think this is a defect and the Honda warranty folks are just using the excuse that I was using a 3rd party mechanic to fix this issue to avoid having to pay for the repairs. I cannot afford this repair $4800. I still have to make car payments as well as the insurance on the car for something fairly new. Can you help in any way with this?