My 2013 Chevy wouldn't pass an emissions test because the check engine light was on. Another mechanic, as well as a dealer service department, had told me I needed a new catalytic converter... apparently based solely on the engine codes. Clark's researched the issue and found that wasn't necessarily true. They instructed me to take the car into the dealer for a software update. The dealer insisted it wouldn't solve anything, since there was no recall, but they went ahead and did it. (Charging me for the privilege... remind me to go write THEM a lousy review next!) I took the car back to Clark's, and after replacing a few sensors that were bad, doing some more research, and putting the car through its paces to allow the diagnostics to reset, the problem has cleared up and the car now passes emissions just fine. They could have just smiled and put in a new part, charging well over a thousand dollars to do it, and I would have been none the wiser. Instead, their detective work and honesty saved me most of that money and left me a big, big fan. You can bet I'll be bringing my car back here next time I need anything. I can't recommend them highly enough.