P0420 Code... O2 or CAT?
06-23-2009, 06:08 PM
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P0420 Code... O2 or CAT? 2001 WS6 w/ 116k miles on the clock... How do I tell if simply replacing the 02 sensor will clear this code? I have no way to measure O2 voltage to see if it's working. I really hope I don't need to replace the CAT. 
