Catalytic Converter/Engine Light issues - 14' Sierra 1500

[huntster21]

Little over a month ago my engine light came up and got the code checked and was both Catalytic converters. Got both replaced and the guy at the shop told me that I had a third one and that GM did that based on where it was made (Mexico) not sure if that's true. Told him I didn't have time to get the third one done and would come back if the light came back up. So it did and went back and was told that even if I do the third one it won't fix the light. If that's the case does anyone know if you can just cancel it then? If not is that maybe the reason the lights still on?

 

Besides that, I was told I just needed a gasket for the passenger side one cause that could be why the light came up in the first place cause its leaking air and would need to replace, but the driver side was fine but its already purple after a month. He told me the reason for that is either miss firing, running rich or just running it too hard. If that's the case wouldn't both turn purple or the passenger side wouldn't cause its possibly leaking between the gasket? 

 

Any help would be appreciated!

[durandetto]

Sounds like the mechanic is clueless. Cats don't generally fail for no reason, depending on the mileage. A misfire can cause too much fuel in the exhaust causing them to fail and an exhaust leak can cause extra air being read by the downstream oxygen sensors making the computer think the cats failed. The third cat isn't monitored by the PCM so it wouldn't throw a code unless it was clogged causing a restriction in the exhaust. If that was the case you would be experiencing a lack of power.

If the shop used aftermarket cats they might not be of good enough quality to keep the cat efficiency codes from coming back. You'll probably need to have dealer cats installed and I would make the shop refund you the money for the cats they installed. Whatever you do I would have a more competent mechanic diagnose your issue. Good luck.

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