My check engine light came on in my 2002 Subaru Outback Wagon after 96K miles. The dealer says I need to replace the catalytic converters. The diagnostic code is P0420. I’ve been told that the sensors could be out, or the root cause should be investigate before spending a bunch of money. Any advice?
Replace the rear oxygen sensors first. They are sending the signal that is condemning the converter. Oxygen sensors have a design life of 100K miles…Is your car subject to emissions testing?
I agree. Replacing the cats will just increase the dealers bottom line. The sensors are usually at fault but they cost less so the natural inclination for the dealer is to replace the high cost components.