I know it's been a while since OP put this up, but I'm wondering if this was figured out/solved. I had this last night driving. I have a 2010 5.7 V8 Hemi with just over 83k on it. Last night driving, she smelled like rotten eggs. I didn't get any CEL and it went away after driving for a bit. It would be nice if it was the battery. If it's the cat I'm going to have to do some planning. I just had surgery on my dominant hand and I'm in a cast until mid Nov.