: Replacing o2 sensor on a 97 deville

09-09-04, 03:26 PM
One or both of my o2 sensors have gone bad. Im getting terrible gas milage and need to change them out. Where exactly are they located at ? I plan on doing this myself and told it was fairly easy to replace so I dicided i would do it myself. Is it just remove and replace or would I have to do something else ? Sorry for all the questions but I want to do it over the weekend so I can get her ready for the road again before monday. I can buy the sensors at my local dealer correct ? Thanks

09-09-04, 09:07 PM
I hate to be the bearer of bad news but there are 4 O2 sensors. One on each exhaust manifold. The rear one is a bitch to get at. Then there is one pre-cat and one aft-cat.
Yes just R & R like a spark plug. I think there is a special socket that makes it easier. Seems to me I had once heard they are $80 each. Rather than just throwing parts at it, run the diagnostics. A bad O2 sensor will set a DTC. Bad milage may also be caused by a leaky FPR. Pull the vacuum hose off of it while it is running and look for any fuel leaking out of the nipple. There should be none. If any fuel is leaking, it is going straight into the manifold unmetered and could be the cause of bad milage as well as a faulty O2 DTC. I would check that first.