I just replaced the front Oxygen sensor on our 2015 Crosstrek. I picked it up with 92.5K miles. It's going to my kid and I don't know when I'll be able to get it again to work. He's away at college and this is something I like to do between 90 -100K miles on all my Subaru's. Like anything it can degrade with time and can start to cause low MPGs. This is a good video about the sensor if you care to look
>>Mr Subaru O2 sensor vid<<
This is the front sensor: Denso 234-9138 Air-Fuel Ratio Sensor, it's an OEM direct replacement.
Install was pretty simple.
Get the car on Ramps and remove the bottom plastic engine cover. It's held on with two bolts in the front and two in the rear, 12mm
One each side left and right there are three plastic fasteners, pop the center out a 1/4 inch and then remove the whole fastener. Small flat blade screw driver works well for this.
There are some little hook/tabs at the rear that hold the plastic cover up, unhook and put the cover aside.
With some needle nose pliers or with a flat blade screwdriver, undo the one little plastic fastener holding the wire to a metal tab. it's okay to destroy this plastic wire fastener as long as the sensor you got has one already installed like mine. If not odds are you are going to destroy it anyway, it was a bugger to get off there for me. You can always just wire tie the wire to that hole if you need to later.
In order to remove the plug from the harness you need to press the tab on the gray harness plug (see pics) then pull the plug off.
Removing the sensor isn't difficult. There is a special oxygen sensor tool that lets the wire hang out when you remove it. There are two types that I know of a slotted one like in the photo and a crows foot one, the slotted on works best here I think. You don't really need to buy the tool, most auto stores will lend you the tool free with a refundable deposit.
I put a few long extensions on the socket and removed it from above, once you get it loose, you can spin it off from underneath.
The new sensor usually has a plastic cover on the threads to protect the anti seize that's already applied to the threads for you. Try to not get that on the sensor probe.
Screw in the sensor, start it by hand so you are sure it's not cross threaded. Snug it down, it's got a crush washer just like the oil plug or spark plug so you don't have to go crazy tight.
Below are a few pics
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>>Mr Subaru O2 sensor vid<<
This is the front sensor: Denso 234-9138 Air-Fuel Ratio Sensor, it's an OEM direct replacement.
Install was pretty simple.
Get the car on Ramps and remove the bottom plastic engine cover. It's held on with two bolts in the front and two in the rear, 12mm
One each side left and right there are three plastic fasteners, pop the center out a 1/4 inch and then remove the whole fastener. Small flat blade screw driver works well for this.
There are some little hook/tabs at the rear that hold the plastic cover up, unhook and put the cover aside.
With some needle nose pliers or with a flat blade screwdriver, undo the one little plastic fastener holding the wire to a metal tab. it's okay to destroy this plastic wire fastener as long as the sensor you got has one already installed like mine. If not odds are you are going to destroy it anyway, it was a bugger to get off there for me. You can always just wire tie the wire to that hole if you need to later.
In order to remove the plug from the harness you need to press the tab on the gray harness plug (see pics) then pull the plug off.
Removing the sensor isn't difficult. There is a special oxygen sensor tool that lets the wire hang out when you remove it. There are two types that I know of a slotted one like in the photo and a crows foot one, the slotted on works best here I think. You don't really need to buy the tool, most auto stores will lend you the tool free with a refundable deposit.
I put a few long extensions on the socket and removed it from above, once you get it loose, you can spin it off from underneath.
The new sensor usually has a plastic cover on the threads to protect the anti seize that's already applied to the threads for you. Try to not get that on the sensor probe.
Screw in the sensor, start it by hand so you are sure it's not cross threaded. Snug it down, it's got a crush washer just like the oil plug or spark plug so you don't have to go crazy tight.
Below are a few pics
