Hi. Scootty.I have a question about my car's checking engine light was on. My Audi S5 2009's engine light was on so I got it checked at authorized Audi Service and they told me the problem was catalytic converter malfunctioning, which was recalled by Audi, so they did it for free. But later they called me saying replacement was completed but the engine light returned after technician doing road test. They diagnosed again and multiple codes came up. The most serious one was Engine Knock sensor, which they said was quite severe and was big concerns for me. They asked me to leave the car for them, waiting for further diagnosis.

I was quite dubious about additional problems detected in such a sudden, so I got the car from them today and brought it to three other mechanics to check the engine light. They all told me that the Engine- Knock Sensor was not on at all and one of them did relatively thorough check and found out the Evap Solenoid was unplugged, which was the reason of causing the engine light on again(The mechanic's point of view ) So they plug the solenoid and the engine light was off again..

I have been driving more than 40 minutes after his diagnosis and the light did not go on again.

I am not sure whether Audi shop tried to deceive me by intentionally unplugging the Solenoid and tried to make money out of this. Or does Audi has much more advanced engine check system that detects problems which other mechanics' system can not? I have attached diagnosis results from one mechanics. No results from Audi because they thought repairing was still on progress.

Could you please give me some advice from your renowned professional point of view. I really do not want to ruin my car if engine knocked off without detection. Thanks and really appreciated!

odds are they just tried ripping you off, I've seen that so many times from guys who went to audi dealers and came to me, it comes as nomal to me.

Thank you for replying! I am just wondering if the lights come up again, should I go back to the dealer?( Even though I am skeptic about what they say. Or any locally experienced mechanics can do the engine job?I believe good mechanics like you should be able to most of engine problems as smoothly as dealers do. I am not certain if German car's dealer has more advanced techniques or system when it comes to engine repairing is a illusion or not. I actually watched lots of your video on youtube and one of them mentioned how sophisticated test equipment could be when it comes to checking modern car's problems.(Great demonstration by the way!)