12-03-2007, 12:46 PM
Date registered: Dec 2007
Engine Management code P203B
Hi there, I have a CLK230 and I recently had the Engine Diagnostic light come on my dash. I had it plugged in which gave me the code P203B relating to a Downsteam Oxygen Sensor TCW.
It also showed me a misfire in cylinder 2 and 3, but that was nothing to worry about I don't think as it was just extra fuel.
What I need to know is, how do I know WHICH oxygen sensor needs replacing? And how do I get hold of one of these oxygen sensors in the UK? Everywhere I look online is only for US models (320, 430, 55)
Any help appreciated, I want to get it fixed before I damage my cat converter.