I have mercedes CLk 230 convertable, year 2000, petrol automatic .
I was driving on motor way (High way) for distance of about 40 miles none stop the management lights came ON while driving.
took the car to garage for diagnostic and showed code (P201E catalytic convertor effiency). The code was cleared and I thought nothing of it.
Used the car in town for many months no problem. But when I drove the car on motorway again for distance of about 40 miles again without stopping the management light came back again.

I must tell you that my cat exhaust rattles a little and it sounds like broken exhaust as if there is a hole in the exhaust but in fact there is no sign of hole, rust or damagae from outside. The engine runs smoothly driving or stationery.

people say various suggestions, from changing cam shaft censor, censor before cat, clean MAF, Mass Air sensor, clean O2 censor, injector problem .
it is a bit confusing, isn't it.

Have you experienced this problem ? Do you know what it is or how to solve it.

Thanks everyone