It is incredibly easy to do this repair on your own and should be done every 100k miles. It can be done in 10 min with minimum mechanical know how or experience. By doing the job yourself you can save yourself about $200. In this instructable, I will walk you threw the steps and I will also give you a AC Delco part number for a cheaper O2 sensor than the one you get at the local part store for $160. Its the very same sensor, just $110 cheaper.
Step 1: Materials
Ok, lets get down to business. Here is what your going to need.
1. A 05 Saturn VUE
2. O2 sensor AC Delco Part # 1255-8143 (I got mine from Ebay for $50 new)
3. O2 sensor socket. ($10 from Advanced Auto Parts)
4. 3/8 drive ratchet.
5. 10 min of your time.
(Note: In the picture I am showing the old O2 sensor that came out of the vehicle. I had already replaced it just prior to doing this instructable.)
Step 2: Locate the O2 Sensor
Open the hood. I am assuming you know where the release handle is. If you are unsure of how to open your hood, I suggest you get some assistance with this repair.
Please make sure that the engine is cooled down. We don't want any burns due to this instructable.
Locate the faulty O2 sensor. I have marked on the picture where to look. It is located on the back side of the engine between the exhaust manifold and catalytic converter. ( I would also like to add: This is Bank 1 Sensor 1. If you had a computer scan that said O2 sensor Bank 1 Sensor 2 was bad then you will need to replace the O2 sensor just behind the catalytic converter. )
Step 3: Remove the Bad Sensor
First unplug the O2 sensor. there is a small clip that you will have to lift slightly then pull. After you have unplugged the sensor from its connector, you will have to pry the old connector loose. It is held in by a plastic barbed pin. If you look at your new O2 sensor you will see what I am talking about. It can be rather difficult to get it loose.
After you have the plug loose from the vehicle. You will need to use the O2 sensor socket and ratchet to remove it from the exhaust manifold. Set the ratchet to turn counterclockwise. Place onto the sensor and start turning. It will likely take some effort to remove so don't hesitate to use some force.
Step 4: Install the New One
Get your new O2 sensor and install it in the location you just removed your old one from. Screw the new one in with your fingers, turning it clockwise. Use the ratchet to get it tight. Then push the plastic barbed pin into the mounting hole for the plug and plug the sensor back up. Close the hood and start the car. Start up the car and let run for about 5 min. As long as your car idles smooth and no check engine lights come on. Your done.
NOTE: If you do happen to have a check engine light on. Go have the light reset. It may be in memory from the previously bad O2 sensor and will need to be reset. If it comes back on again, then you should have a tech look at your car. Something else may be going on.