Contour Enthusiasts Group Archives Forums General Troubleshooting Replace O2 sensor when replacing CAT

My check engine light came on and I took it in and was told the cat needed to be replaced. This was covered even though I am past my warranty period. However, I was told that the oxygen sensor should also be replaced (240$ not covered) as a preventive measure. This sounds like a scam so I am asking if there would be a valid reason to replace the sensor when replacing the CAT converter.

In theory a bad O2 sensor could cause the engine to run rich, which could degrade the cats faster.

In practice, $240 is way too much for a $50 O2 sensor that takes 20 minutes to replace.

Brian

Depends - the bank 1 upstream is a real bear to get to. The rest are 20 minute jobs.

Hey Dan I'd ask to see something that shows which one it is, like a code or something, they have to know which one is bad to charge you like that Good luck to you

Basically, they said the CAT was bad, and they recommend the o2 be replaced although they did not indicate they were bad. As some have stated, the engine not running right might be the reason the cat went bad so soon. I am starting to wonder if my motor is fully right as it has gotten poor gas milage from day one (20 city only 25-26 on highway). Maybe that milage is normal, but it seems pretty poor for a 2.5 V6. Also, is it normal for the coolant temperature to rise slowly on the gauge. Mine often takes a few minutes, even with mild temps? Finally, is the O2 something that is easy to replace, or is it best left to a mechanic? Any help is appreciated. F