Below is a video on How To Replace Both O2 Sensors On A Subaru
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Today we will showing you how to replace both your 02 sensor on a 2007 Subaru Outback. We used our Innova 3150d scanner and pulled a P2097 code which is the post catalyst fuel trim system too rich bank 1. Normally replacing the rear o2 sensor will take care of this code sometimes you will need to replace the front O2 sensor or the air fuel sensor.
In this video we are replacing both as this car has 213, 294 miles on it and it just had the head gaskets go bad and replaced so there was coolant going thru the exhaust and getting on the sensors. So to be safe and ensure they don’t have a problem down the road with the other one sensor going bad we are replacing both. When replacing O2 sensors at least with the Subaru’s Still with OEM ones which are Denso’s. These people used a cheaper direct fit one and install it themselves and had more problems then what they started with. It started had, stall out at a stop and caused 3 or 4 more codes to pop up.
So to start well open the hood and then grab a 10 mm wrench or socket and ratchet to remove the positive side terminal off the battery. While your removing the cable its a good idea to look at both your battery terminals for corrosion. If you need to now is a good time to grab a battery terminal cleaner and clean them. We are removing the cable to reset the computer and to remove the check engine light.
Once we have the battery terminal removed we can remove the air inlet from the air box. Some have two 10 mm bolts holding the front to the radiator support and others have two push pins holding it in position. If you have the bolts you can use the same wrench or socket and ratchet we used to remove the battery cable and remove them. Once you have them removed we can lift and pull towards the front of the car to remove the air inlet from the air box. Also a good time to look inside and inspect your air filter.
Once we have the air inlet removed we can locate the sensors and wiring. The plugs are located right near the front passenger side of the car right next to the power steering lines/ pump and the radiator hose. One will be a black and gray plug and the other will be an all grey plug. The black and gray is the front O2 sensor or the air fuel sensor and the all grey one is the rear O2 or post O2 sensor.
Well start with the front O2 sensor or air fuel sensor by pressing and release the clip to undo our wiring connector. Once we have that apart we can squeeze the clip to remove the wiring from the bracket. Now that we have the wiring loose we can grab a 22mm wrench or a crows foot O2 removal tool and loosen the sensor. With the front sensor the plug end is to big so we’ll need to use the open end of the wrench. Well get it on there and loosen and remove the sensor. It may be a good idea to spray it with some Kroil ahead of time to make it easier to remove. If it goes hard make sure to add more spray and work it back and forth. You will also be working on/ right next to the exhaust so you will want the car to be cold as you may get burned when grabbing the sensor.
Once we have the old sensor removed we can grab and unpackage our new one. The part number for the new Denso front O2 or air fuel sensor will be 234-9123. Well add some anti seize to the threads of the sensor be careful not to get it on the sensor. Also when you get the OEM one which may not come on a direct fit one will be the heat disc/ shield and the clip to hold the wire in the bracket. If you think you damaged the treads you can run a 18mm by 1.25 tap though there. Well start the new sensor by hand and get it hand tight. Once hand tight we can grab the 22mm wrench and snug it down. You will also notice that the heat disc doesn’t rattle or move around any longer.
With the sensor tight we can clip the wire into the bracket down by the timing cover and then grab the black plug end of the sensor and plug it into the grey connector of the car side. Be sure to hold the grey connector as you could push it off the bracket or brake the clip.
Now that we have the front O2 sensor or air fuel sensor replaced we can move onto the rear O2 sensor. Well do the same thing squeeze and undo the plug connection. Then move down and undo the clip that holds the wiring to the bracket by the timing cover.
Now with the wiring loose we can either turn the wheel all the way to the passenger side or jack the car up and remove the wheel. Making sure its on level ground and you use a jack stand and wheel chock to ensure it can’t fall or roll. Once we have done that we can locate the small push pin so we can remove it and lower down the panel so it’s easier to get at the rear O2 sensor. Once we have the panel out of the way we can spray the sensor. With this sensor the plug end is smaller so we can use the closed end of the wrench as it will hopefully reduce the risk of stripping it. Once we have the old sensor remove we can grab and unpackage our new Denso rear O2 sensor. The part # for this one will be 234-4445. Next we can add anti seize to the threads and start installing it by hand. Once hand tight well grab the wrench and snug it down.
With the sensor in and tight we can set the wire on top of the cat so we can reach it easily from up top. Next we can reinstall the inner fender panel. Well push it back up into position and align the hole and reinstall the push pin. Once we have that on if you removed the wheel you can reinstall it and torque it down.
Next we can go back on top and grab the wiring and push the wire clip back into the bracket by the timing cover. Once we have that in we can connect the gray plug end back to the car connector. Be sure to hold it so you don’t break the clip on the car side holding it to the bracket.
Now that we have all our wiring connected we can grab the air inlet and reinstall that. Well just push the end into the air box and align the front two holes. Next we can reinstall the pins or the two 10mm bolts using the ratchet and socket or wrench.
Once we have the air inlet installed we can reconnect the positive side of our battery terminal to the battery. Once we have the battery connected. We can start the car and let the car warm up to operating temp and then do some light driving to let it do some learning and a few drive cycles. It may take a few tries to get the car to start as we had the battery disconnected and to get information from the new sensors or run its base trims.
That’s it we have just shown you how to replace both O2 sensors on a Subaru.