My ML320 got Chk Eng light turned on. I did use a diagnostic scan tool to retrieve code and found code P207E (Catalic converter redement too low (P0432) in register. I reset code, and occasionally re-run the diag and found the same code re-appeared but this time there's no check engine light . It might be because the error threshold has not reached to turn on the light ? There's some discussion about oxygen sensor . Can I get some expert opinion on this error code please ? Thanks for the help

 

most of the time when there is a cat efficiency code, the problem is the cat. also some mls have had recalls on the cats. you should check to see if yours has a recall

 

Thanks Alex..
I replaced the downstream O2 sensor and haven't not seen the error for a week. Keep my fingers crossed