This is surely an unfortunate circumstance. When the appointment was made the complaint was, check engine light is on and check charging system, battery goes dead. The technician scan the computer system and found 2 trouble codes one was for the ratio sensor and the other was a crank sensor code. The charging system was also checked along with the battery and the electrical system was check for a battery drain. The vehicle needed a ratio sensor and battery. Authorization were given for the ratio sensor replacement, which is mounted in the exhaust system. The total repair bill was $654.58. After talking to the service advisor at the dealership I was told the engine was knocking possibly due to a spun connecting rod bearing or piston wrist pin, he also said the engine was full of oil. From my experience as a technician for over 30 years, it is impossible that replacing the ratio sensor in the exhaust system would have damaged the engine. You are a valued customer and have been for many years. I am sorry that this happened and I feel we are being wrongly accused in this situation.