summit151

It certainly is a head scratcher. Driving me crazy. She said it smells kinda like rotten eggs. I just smelled a exhaust smell when I got it to act up

Hey everyone so my friend has a 2018 GMC Yukon that only has 30000km on it and since August she has been getting a intermittent very bad exhaust smell in the cab. She has taking it to severely dealerships and they can not find the problem. It only happens once in awhile while driving it. I recently took it for a drive with my personal gas monitor that reads CO and it it started to read a very large amount of CO when I was test driving it and I could smell it very easily. I the took it back to one of the dealers and took a tech for a drive with the monitor and of course it didn’t get any smells on the cab. I tried to change the setting with the heater controls and recirculating air control and it didn’t help. She now has called me again saying it was very bad on the way to work again. The dealerships said they have gone through everything possible? I mentioned maybe a manifold leak but the said it would be noisy if that was the case. I am wondering what could have been missed that I can look at? And what is the best step going forward?