2001 Nissan Xterra pro 4X what would cause the check engine soon light to stay

Hello, Dave here, contributing to RepairPal and providing expert advice since 2010. The information you received from the repair shop is not accurate. Just because the catalytic converter's are aftermarket, if they are proper for the vehicle they should do the job that they are made to do and you should not have a warning light. However my guess is that you may be using aftermarket sensors that are not reporting information properly and could be causing the problem to continue. All that said, I don't know anything about the trouble code your vehicle has. A check engine light will serve as evidence that there are diagnostic trouble codes present that provide information for technicians that help to diagnose and repair the vehicle. You really need to have a shop look at the vehicle that knows what they're talking about! It is not acceptable to have a vehicle that has all this work done and still have a warning light. It does need to be resolved. I would recommend a second opinion of a shop near you. Check below -- https://repairpal.com/auto-repair-near-me Click the link or call us at 877-913-1554. We'll gladly find you a certified RepairPal shop in your area.