CEL Flashing Code 420...Help
I have a 2000 Forrester that is flashing a CEL code 420 ---inefficient catalytic converter. I just had the 60,000 mile service on it but did not replace the front 02 sensor or the rear one. The mechanic thinks it is the catalytic converter that needs to be replaced. He got the CEL light to switch off but wants to run it to see if it comes back on and then rediagnose it again. My bet is that it comes back on. What do you guys think? Is it the catalytcic converter or the O2 sensor(s) or something else? What should the next step be in your opinion?