I got the check engine light to go out after replacing the front oxygen sensor. I replaced the rear as well since the 1998 Forester has 133,000 miles on it.

 

I read somewhere that if the car's computer does not detect the code after running the car three times, the check engine light will go out. The error code is stored though. So I started the car four times not having much faith the light would go out. I was so pleased when the light did not come on with the fourth start.

 

Both sensors came out easily. I sprayed a bit of PB Blaster on the day before.

I thought the 420 code was a smoking problem...?

I thought the 420 code was a smoking problem...?

 

Ha Ha. I need to replace my O2 sensors as well.

I have this code with my 01 Forester with 167,000 miles on it.

 

Is the front 02 sensor something easy for someone who is not a mechanic (ahem, meaning myself) to replace? Where is it on the car?

 

ALSO IF I need a cat, can anyone post a non-ebay link to a cat that will work on an 01 Forester besides the OEM (expensive)

Front o2 sensor is in the exhaust pipe near the front cat. It isn't too hard to change. The hardest part can be freeing up the existing o2 sensor. Spray with penetrating oil a day or two before the job. Usually it's easier to free up with the exhaust a little warm than cold.

 

Unhook the connector. Then feed the wire through a 22mm or 7/8" 6pt wrench. Tap the wrench with a dead blow hammer. Don't be too rough on it because you don't want to mess up the bung or break the sensor off in there.

 

Also exhaust leaks can cause o2 sensor codes.

[...]Also exhaust leaks can cause o2 sensor codes.

Some more on the topic: http://www.motor.com/MAGAZINE/Pdf/102006_09.pdf