2002 Pontiac Bonneville Running Lean

Hi:
Are you sure it's the O2 sensor? Usually the code will indicate a bad one. I would start by checking for vacuum leaks. What size engine do you have?

As far as the O2 sensor, it's on the exhaust before the catylatic converter.

It is a 3.8l V6 in the Pontiac SE. I orignally was getting the code for the bad IAT sensor and that it was running lean. I replaced the IAT sensor and checked the hose which that sensor it hooks into for leaks. There aren't any leaks in that hose.

Which other hose(s) would be likely to cause this error?

I hate to say it, but you need to check them all. Any vacuum leak will allow air into the engine which will cause a lean mixture.

With the engine running, do you hear any hissing sounds?

I will check tonight to for any noticeable hissing sounds, but I know when I was working on it previous I didn't hear anything, but it is quite possible that I just didn't hear it the first time. Thank you for the reply. I will take a bottle of soapy water to the hoses and see if I can find where any leaks are.