How do you replace the oxygen sensors on a 2002 forester they both need to be replaced?

Answer 1

the O2 sensors are located under the car on the exhaust system. It looks like a large bolt with a wire coming out of the top. The one before the cat (bank 1 sensor 2) is in a funky place, and you will need to remove the heat shield around the exhaust pipe. This is 5 bolts- 4 take a 12mm wrench and one takes a 10mm wrench (?!)- whatever. Use a bunch of WD40 and let them soak for a little while, because they will be rusted and stuck. You won't be able to completely remove the top of the heat shield, but once it is loose you can get to the O2 sensor. Use a crescent wrench (or appropriate size metric wrench- I think it is a 20 or 21mm wrench), and gently give the O2 sensor a little twist. Now, go back up top and disconnect the cable that leads to it... it is under the right (passenger) side of the air filter housing. Look for the green inner CV joint and that's where the cable is. The connector has a grey plastic piece that flips back a little and releases the sensor half of the connector. Undo the connectors, go back under the car, and finish unscrewing the old sensor. Reverse the procedure to reinstall. I just followed the instructions above on a 2001 Forester and they proved accurate. I would add just a few points. On my Forester there were five 12mm bolts on the heat shield. Also apply WD40 around the old oxygen sensor gasket because the sensor may not break loose easily. After applying the WD40 go off and have a coffee, as I found it took at least 15 minutes to penetrate. Even so, I found I needed one good rap with a lead hammer on an open ended wrench to free the sensor. Significant hint: when disconnecting the cable connector, loop a string around the sensor plug before letting it drop down in order to remove it. You can then use this string to bring the new sensor cable up via the same route as the old one went. Also, definitely put anti-sieze compound on those heat shield bolts before putting them back on!