Oxygen Sensor (Upstream) Replacement ... 2003 Subaru Baja

[OkeefenokeeJoe]

I own and drive a 2003 Subaru Baja with 171,000 miles on the clock. It is my daily driver and runs like a champ. Several weeks ago the "Check Engine" light popped on as I was driving from work. Turns out the culprit was a faulty upstream oxygen sensor. I took it to my local stealership and they wanted $218 for the part, and an additional $250 labor to install it. "Crazy," I said, and decided to try to do the work myself. Although I am NOT mechanically inclined, I figured this could not be brain surgery.

The Subaru Part # for the upstream oxygen sensor on the 2003 Subaru Baja is 22641AA280, and is manufactured for Subaru by DENSO. After a diligent online search, I found the exact Subaru part, but under the DENSO label, at Amazon. The DENSO Part # is 234-9015. It is an "exact fit" replacement .... plug-n-play. The price ... $87.99 .... less than half what the dealership wanted for the Subaru-labeled exact same part. It was a freakin no-brainer, so I ordered it. The part arrived today about lunchtime.

REMOVAL OF OLD SENSOR:

This afternoon I got out my Chilton's repair manual and located the oxygen sensor on my Baja. I found the oxygen sensor on the passenger side of the Baja. It was protruding from the front side of the exhaust manifold. In order to facilitate removal of the oxygen sensor, I got out my floor jack and raised the right front of the Baja, then removed the tire and wheel to allow better access to the oxygen sensor. Once I got the tire and wheel removed, I sprayed some penetrating oil on the base of the sensor (the screw-in part) to ease removal. While the penetrating oil soaked and ... ummmm ... penetrated, I removed the battery cable from the negative terminal from the battery.

Now ... the Chilton's manual suggests that to remove the oxygen sensor you need an offset oxygen sensor wrench. Not so. the space around the base of the oxygen sensor is so confined on the 2003 Baja that an offset oxygen sensor wrench is rendered useless. I ended up using a standard 7/8 inch SAE open-end wrench to loosen and unscrew the oxygen sensor, which worked just fine. The oxygen sensor actually unscrewed rather easily. I was anticipating a struggle, but (fortunately) that was the case.

The opposite end of the oxygen sensor is an electrical plug-in connector, connected by a "pigtail" of approximately 12 inches. The electrical wire and connector worms its way upward, into the engine area, and is best accessed from the right hand side of the engine compartment, from under the hood. I had a little difficulty, at first, getting the electrical connection on the old sensor to separate, but using a small flat-blade screwdriver to "encourage" the separation from the male end, the connector finally loosened and detached. I then fished the old sensor, in its entirety, from underneath the car and examined it.

I compared the old Subaru sensor to the new DENSO # 234-9015 replacement sensor that I purchased from Amazon. They were exactly the same in every detail. The only exception being that the pigtail (wire) on the old sensor was yellow. The pigtail on the DENSO replacement sensor was black. The electrical connections were exactly the same on both.

INSTALLATION OF NEW SENSOR:

The new DENSO sensor came supplied with a small tube of anti-seize compound, which I smeared on the threads. I then, using the 7/8 inch open end wrench, carefully screwed the new DENSO replacement sensor into its location in front of the manifold. Yes, the area was very confined and difficult to work-in, but with patience I managed just fine. I then snaked the electrical connection and pigtail up into the engine compartment, being very careful to follow the exact route of the old sensor. The new connector plugged in rather easily and snapped into place with no problems. I then reconnected the battery cable to the negative terminal of the battery.

At this point, installation was complete.

I then turned on the ignition to check the dash and ... TAH DAH ... no check engine light!

Total time ... start to finish ... approximately 45 minutes for a complete doo-doo head novice (me) doing all the work with absolutely no assistance.

I hope this helps someone with the same issue. YES!!! ... you can do it! Freakin piece of cake!

OkeefenokeeJoe

[hocrest]

Great write up.

One suggestion I'll add for a situation that you luckily didn't have to deal with. If you have trouble unthreading the sensor and there is ANY rust on the threads, there is an additional step you should take. As an owner of older Soobs in the NE, I seldom have one unthread cleanly.

Get a O2 sensor thread chaser. This tap made to clean out the threads of an O2 bung. Most autoparts stores will have one for about $10. If you reinstall your new sensor without cleaning the threads first, next time you go to remove it, chances are good that you will damage the bung.

[mladen99]

great, next time do a few photos.