Trying to help out someone out. This car has an O2 sensor light that is not lit but the CEL is on. Most probable cause? Can I take it to autozone or similar to check code, or is this a MB only diagnosis. I really do not know where to start, it is running fine, low idle perhaps the only thing I notice . HAs 128K on the clock

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Ron
2015 Porsche Cayman - Elizabeth
2011 Porsche Cayman - Bond,James Bond
Sadly MERCEDESLESS - ALways LOOKING !
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