[Joshinator99]

Originally Posted by KingLT1

That code normally means there is a leak in the exhaust up by the second o2 sensor on bank 1. my guess the leak is at the slip connection.

This ^^^

[Diamond]

Originally Posted by Diamond

I bought my 2018 ZL1 from a Chevrolet dealership on 23 Jul 21 with the with an AWE cat-back Touring exhaust already installed by the previous owner. The dealership Certified the car (172-point inspection). about a week and a half later the engine check light came on with the P0420 code. I reset it to see if it was just a fluke. 1 week later the light, and code was back. I took the car to another (much closer) dealership and they replaced one of the O2 sensors. I didn't get 5 miles from the dealership and the light, and code was back. I took it to back the dealership and this time they replaced the catalytic converter. I didn't get 2 miles from the dealership and the light was back on. I took it back to the dealership and they "discovered" a clamp on the bank 1 side catalytic converter was missing. When the 2nd (correct) clamp came in i brought the car in this morning to have it installed. They completed the work this morning and charged me $177 for the "missing" clamp. I didn't get 3 miles from the dealership before the light, and code was back.

I contacted AWE about the issue after the catalytic converter was replaced and they tell me they never see any issues or codes with this system. The dealership is now telling me they have done all they can.

My only recourse at this point seems to be for me to find a competent shop that can troubleshoot the issue. I plan on taking it to one next week. Just wondering if anyone on this forum has had this problem.

Update 9 Dec 21:
I took it to a great muffler shop and they found multiple leaks at the catalytic converter (Bank 1). I asked them to remove the clamp and weld it together. They reset the computer and the problem is gone. Thank you all for the great advice and help!

[KingLT1]

[arpad_m]

Originally Posted by Diamond

Update 9 Dec 21:
I took it to a great muffler shop and they found multiple leaks at the catalytic converter (Bank 1). I asked them to remove the clamp and weld it together. They reset the computer and the problem is gone. Thank you all for the great advice and help!

KingLT1 nailed it again, as always Honestly, we should have a "send a beer" feature on this forum so people can express their gratitude.