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Catalytic Converter in 2002 Subaru Forestor

I drive a 2002 Subaru Forestor with about 134,00 miles on it. Earlier this week the check engine light came on. I took it to the dealer and they said the code read that the catalytic converter had fallen below efficiency. The repair cost, including labor, was to be about $1000. The mechanic did tell me that I could continue to drive it as it is, but at some point - maybe two months, maybe two years from now - it would start to cause me problems. He also cautioned me against any after market catalytic converters, saying he had seen those not last very long.

I’ve done a little research of my own (though I understand very little of it because I know very little about cars!), and it sounds like I can indeed likely go on for a long time without this really being a problem. It also sounds like it could be something else besides the catalytic converter (such as the O2 sensors, which the mechanic never mentioned). I’m wondering if anyone has any insight on whether or not I should make this repair right now? I’d like to keep this car for another 100,000 miles if possible, and I’m worried that if I don’t get this replaced soon I will cause further damage to the car. I’m also in poor health, and regularly drive long distances, and I’m worried about being stranded someplace because of a car problem. That being said, I really don’t want to shell out $1000 for an unnecessary repair.

Any input is appreciated – Thanks!

I forgot to mention that another mechanic suggested I just get a bottle of Techron and start using a better quality gasoline… Any thoughts?

Hi AJL117, Shakeman from the forums here … your plight amongst aging Foresters is not uncommon and we have fixes for it. What happened is the pre-cat Air/Fuel O2 sensor after 10yr/100,000miles of use becomes worn-out and begins to run a rich Air/Fuel mixture. In doing so the cat. and the post-cat. O2 sensor became dirty and thereby caused a cat. inefficiency error code. There are few things you should/could do.

  1. Inspect the post-O2 sensor for broken wires or bad connections. This alone could be causing your OBDII error.
  2. Remove the post-O2 sensor and generously spray it with electrical contact cleaner and compressed air. Do not scrape, scratch or brush the sensor. Re-install the sensor and clear the OBDII. Autozone or AdvanceAuto will clear it for free.
  3. Remove and Replace the old pre-cat Air/Fuel O2 sensor! The new O2 sensor will increase your MPG and over all performance of your car! Forum members have determined the old, worn-out pre-cat O2 sensor are causing all sorts of head aches without causing any ODBII errors.
  4. Spiritedly drive the car for a while in order to blow the carbon out of the catalytic converter.

Best, TonyS

Won’t driving w/o pre-cat sensor trigger the CEL?


Your question, “Won’t driving w/o pre-cat sensor trigger the CEL?” makes absolutely no sense when referencing the original post and my response. But, to answer your question, yes, and in addition the car will run very rich. Running without a O2 sensor is not a good idea.

Best, TonyS

Don’t run a cleaner until after you clear the codes. The last thing you want is more debris, carbon or dirt, flowing through your exhaust. After you get straighten out then run a cleaner like Techron twice a year as a general maintenance to keep your fuel system up to snuff.