Catalytic Convertor problems of the 2017 Hyundai Sonata

The contact owns a 2017 Hyundai Sonata. The contact stated while driving at an undisclosed speed, the vehicle stalled with the check engine warning light illuminated. Additionally, there was white smoke coming from the engine compartment and the exhaust. The contact retrieved dtc code: p0420 for spark plugs failure. The spark plugs were replaced; however, the failure reoccurred. The vehicle was diagnosed with spark plugs and catalytic convertor failure. The spark plugs were replaced. The contact stated that the spark plugs looked burned. The vehicle was taken to an independent mechanic where the catalytic convertor was replaced; however, the failure reoccurred. The contact stated that the vehicle was consuming an excessive amount of engine oil for almost two years. The contact stated that engine oil was added every 600 miles of driving. The vehicle was not diagnosed or repaired by an independent mechanic or the dealer. The dealer was made aware of the failure and provided the contact with the cost for a diagnostic test. The contact declined to pay for a diagnostic test. The manufacturer was made aware of the failure and a case was filed. The failure mileage was unknown.