Catalytic converter is damaged when you remove and clean it with especially acids, "tezaab"
Most mechanics do this, which damages the net "jaali" in catalytic converter and due to which you face engine check light issue. Never go for these 3rd class mechanic who plug out Catalytic converter and clean it, there's a 99% chance you get that engine check light. Try to go with machines. I went with machines, didn't give me a result,but my catalytic is in perfect condition, no check lights. You can try to replace parts in catalytic which will not be for long term and you will keep seeing those engine lights after a few days. Better is to replace the whole of catalytic at once which is also available at pakwheels auto store
