Catalytic Converter Inspection

If excessive exhaust system back-pressure is suspected, remove the TWC from the vehicle.
Using a flashlight (A) and plug (B) (KG, KS, KE, KR, KU, KZ, FO, KQ models) make a visual check for plugging, melting or cracking of the catalyst.
Replace the TWC if any of the visible area is damaged or plugged.

KG, KS, KE, KR, KU, KZ, FO, KQ models: 

KN, KM, KY, MA, PH, IN, KK models: