o2 sensor questions

[Everhutch]

I have tried searching, but can't quite figure this out from the questions that were asked/answered before. I have a 96 m5 Camaro.

I got codes 102 and 133 on the OBD2. One is the o2 sensor and one says it is the MAF. Does the 96 have a MAF sensor? At Autozone there was no MAF part for my car and there were indeed 2 different o2 sensor part numbers. Bosch 15703 ($49.99) reads "before the cat" and Bosch 13111 ($74.99) reads "after the cat."

Also, should I replace them both? Or is there any reasonably easy/inexpensive way to check which one it is? or for the trouble should I just change them both?

Someone posted that they are the same... but I have no idea. Please advise!

Also, can a bad cat foul an o2 sensor? or do they just go bad over time regardless? The reason I ask is because I want to put in a high flow cat soon... should I do it before I swap the sensors or does it make no difference?

I know there are a lot of questions in there, but any help would be great.

Thanks

[vtv6firebird]

The 3.8 liter does have a MAF sensor it is the first thing in the throttle body, right before the butterfly.

There are 4 O2 sensors.
right manifold
left manifold
right before the cat
right after the cat

the code 133 refers to bank 1 sensor 1, which is on the left manifold I belive.

The manifold O2 sensors are differnt then the ones at the cat.

In Autozones computer one of the two should say "two required", standing for right and left manifolds.

The manifold 02 part number is Bosch 15703
you might as well replace both now. You will get better gas milage anyways.

The pre cat and post cat O2s are both
Bosch 13111 These only check the operation of the cat, so I wouldnt worry with replacing them unless you start to get errors from them.

O2 sensors just go bad over time, with wear and age, I doubt a bad cat would mess them up, but a bad cat will cause error codes from the post cat O2 becuase it is showing the cat is not doing its job.

If you really want to replace all 4, then go ahead, but I would prob just wait till you get the new cat to replace the cat O2 sensors.

Damn GM just had to put 4 O2 sensors in our cars.

If you have anymore questions, just let me know.

And if anyone finds a mistake in my answer let me know as well.

[Everhutch]

Thanks, I think I will replace the 2 manifold ones. If that doesn't fix everything, I will change the others with the cat. That sounds like a plan. Thanks a lot for the response. If I could trouble you one more time... do you know the easiest way to access them? i.e. where are they exactly? I'm sure I could figure it out, but any help will only make it easier!

[vtv6firebird]

OK, as far as accessing them I am not sure. I am getting ready to replace mine in the next couple of days. I would say reach from under neath the car. I can only reach the drivers side from the top. The passenger side i couldn't even feel the sensor, but there is no way i could even get a wrench on the drivers side, plus the connectors seem to be somewhere on the back of the engine.

And they are just about midway down the manifold before it attaches to the y-pipe. Only sensor on the manifold, so you cant miss it.

Good luck