tomscia

I need to replace the oxygen sensor on my 1991 300SL. I have done this before on other cars I've owned. However, I cannot even locate the ox sensor on my 300SL. I've heard that access may be from under the floor or seat on the passenger side. Please advise. Thanks, Tom

sl3204me

If yours is like my 1995 SL320,one oxygen sensor is before the catalytic converter in the exhaust pipe and goes into the floorboard in the passenger floor under the carpet.The 2nd O2 sensor is after the converter in the exhaust pipe and connects to a connector under the car.If you are not sure if they have been replaced in the last 50,000 miles or so,I would replace both and also clean the heat filament inside your mass airflow meter with electrical contact cleaner.This will keep your emissions system in good shape.Prevents the check engine light from coming on and the car going into limp home mode.Don't forget to check the air filter also.Keep it very clean.

LeaUK

Mine has only one O2 sensor before the CAT (Europe regs) but I while back I bought an OEM replacement only to find it's a complete pig to get at. So when reading this post I'm excited.

Can you get to the O2 sensor before the CAT from inside somehow - has anyone got any pictures?

Cheers
Lea