[Ohshtkevin]

I have an 07 335i my cobb access port reads P2C9E "Lambda sensor heating the catalyst 1, triggering" it then goes on to say that this is typically caused by a failing 02 sensor.

This code started when I got the four bolts connecting the downpipe to the rest off the exhaust blown off with a torch so i thought it was just caused by the exhaust leak made thereafter. I drove my car home slowly less than a mile from the shop that blew the bolts off for me. I then installed my new AA dp and the code is still there even after clearing it.

Do I have a bad 02 sensor or could it be something else? And if it is an 02 sensor how should I go about figuring out which one it is?