I've been throwing CELs lately but I thought it was because of my midpipe. I'm going to check my gas cap and if that doesn't help, I'll take it to the dealership.

I'm glad I read this thread... good posts guys.

 

My CEL has been coming on and off for the past two weeks. I finally took it into the dealer and without them even doing a diagnostics check told me it is most likely due to my aftermarket (Borla) cat back exhaust. Is this a ligitimate remark or should I question them further. I told them to run the diagnostics and get back to me.

 

I doubt a different cat-back exhaust would directly cause a CEL. Make sure you get the DTC error number from them when they report the results of their diagnosis. Then check the DTC list on the forum (link below) for an explanation of the error . I suspect they are preparing you for denying a warranty repair. If their diagnosis shows an error that is obviously unrelated to the cat-back, calmly indicate to them that you do not accept that it was caused by the aftermarket exhaust system and if they don't come around, call Mazda North American Operations (800-222-5500) immediately to explain the problem and to seek their assistance with getting the problem resolved. That's straight from the owners manual, BTW.

DTC List: https://www.rx8club.com/showthread.p...ight=DTC+codes

 

Well, the dealer came back to me today and told me the DTC code registering on the diagnostics is "P0420 Catalyst system efficiency below threshold ON 2 Catalyst ", told me my cat needed replacing, and that it was due to my cat back exhaust system. I'm wondering if this may be due cold weather but I don't know, I'm having a hard time believing that my cat back exhaust system ruined my cat. Any ideas?

 

tell them to prove it and show them a copy of the magnusson moss act- if you are in the USA

 

Cold weather had nothing to do with it. Failed cats are, unfortunately, not too unusual with this car. You can search the forum and read many posts about just that. Your cat-back exhaust did not caused the failure, and I would make that statement to the service manager. If they refuse to replace the cat under warranty, call MNAO, explain the standoff to them and request that they intercede on your behalf.

 

Well, called up MNAO and filed a complaint with them on the issue. They said they would have an analyst investigate the issue further and get back to me. We'll see what happens.

 

Good on ya. The dealer will be calling you very soon. Let us know the outcome, please.

 

nonsense.... exhaust system never fail any CATpipe.

 

Just thought I would add a little update, the CEL came back on again about two weeks ago. This time I took it to a different dealership, they told me the problem was the same, the CAT and seal were bad, but they said they'd replace it no problem under warrantee. It sucks that dealerships can be so different.