Thanks guys,
I just recently replaced the O2 sensors and the error came back and I noticed the foul (rotten egg) smell. I am not sure if it smelled like that before I changed the sensors, it probably did.
So as I understand it may be the cats. But how can I test?
regards,
Sab.

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regards,
Sab.
'07 ML320 CDI (398 ft lbs / 1400 RPM)
'02CL 500
'91 928 GT Supercharged