My 2002 e320 suddenly started making a rattling noice at idle. Car has 110,500 miles on odometer.
I crawled under the car, and the sound is coming from inside the rear of the front resonator.

I've read that rattling can be the first sign of a dead catalytic converter, but is this true from the back end of the front resonator?

Have you encountered this?
Any suggestions for fixing it?

I'm going through vehicle inspection (including emissions testing) in about ten days, so I'll know if my converters have failed. If they are ok, does it make sense to cut open the back of the resonator, empty the debris, and weld it back together?

 

For me the rattling turned out ot be the converter. I just unbolted the back of the exhaust, beat the honey comb debris into smaller pieces and kept starting the car until I blew it all out. That was months ago and I have never popped a code and it passed emissions.