Im need to change the oxygen sensor on my 97 bonneville SSE. The diagnostic says that it is the bank 1 sensor 2. My question is where is this sensor located. i have read several posts on here and some say there is only 1 sensor before the converter but that doesnt make sense to me. So can someone please give me a little advice that would be greatly appreciated. Thanks,
brett

the first sensor is right behind the engine, in front of the firewall right on the exhaust manifold...

the second sensor is underneath the car past the cat...

but if its giving you a code for the second sensor post catalyst, its telling you that you need to replace your cat most likely.

Is there any way to clear the check engine light without replacing the cat?

Could it mean that the sensor is bad? Does that happen, my car has about 200,000 milles on it and ive had it sense about 50,000 miles and have never changed it. Is this a possibility?

now why would you want to do something like that?

its telling you that your cat is not functional anymore and basically that its clogging. the result is lost power, increased emissions, overheated exhaust and i do believe, but not sure, decreased gas mileage.

but if you must...
you can reset the computer by unplugging the battery for about 15 minutes...that'll tell you for sure if theres something wrong if it comes back

edit: yes, you should change your FIRST 02 sensor every 100k, the back one I don't know whether or not it should be changed, but my understanding is that is does not, and is only there to tell you if the catalyst is operating properly.

and just so you know...one of the best ways to clog a cat is to have a malfunctioning #1 o2 sensor. the rich exhaust fumes clog it up even faster.

looks like you've got two things on the list. but first, change that o2.

second edit: WHILE we're on the topic. you've had this car for 150k. since you haven't changed the o2....have you replaced your upper intake or lower intake manifold gaskets before? if you're burning coolant, thats another way you could murder a cat.

thanks for the advice

note my second edit. its quite important and could cost you an engine if ignored.

no I have not changed either the upper or lower manifold gaskets. It doesnt seem to be using up coolant so how would i know if i need to replace the gaskets?

It could just as easily be the rear O2 as well as the Cat. Get a backpressure test done on the CAT.

And yes, you need to take care of your UIM and LIM gaskets before you motor goes POOF.

http://www.bonnevilleclub.com/forum/...e=article&k=38

Read that article.

if the O2 sensors are bad will the check engine light go off right away after you replace the sensors or will it take a little while?