my four maun problems with my 03 pontiac bonneville . 1st. off i changed o2sensor twice and now light is back on .2nd front motor mount is busted can that be why light is on. 3rd. i need a new wheelbearings for one of my front wheels.can this be why i am getting a squelling noise. i put raybestos ceramic pads on what would be excellent rotor to use to accomidate them. i need something that will not rust and make that horrible squelling noise. i forgot to mention why is my car hesitating i had it scanned at autozone 3timesand the only code i am getting is o2sensorcode in bank one.i took it to a transmission shop and all they said was i needed to get my motor mount fixed. they also told me i need a tune up to stop hesitation. i only have 76000mi.i thought u get a tune up at100000mi. if i need a tuneup what all comes with a complete tuneup.

first off, http://www.bonnevilleclub.com/forum/...ic.php?t=73691

next, what brand oxygen sensors are you putting in? Our cars do NOT like Bosch, so if that is what you are using, get a new AC Delco unit from the GM dealer.

next, replace your worn out front motor/trans mount with 3 hockey pucks, it works like a charm, as seen here: http://www.bonnevilleclub.com/forum/...ockey&start=40

A good tuneup would consist of:
Oil change
Oil filter
Fuel filter
Air filter
Spark Plugs
Spark Plug Wires
PCV valve
etc...

On the O2 sensor code. Have they told you the code or just that it'* an O2 sensor needing to be replaced? Because a lot of codes will be interpreted by the parts puppies incorrectly. For example, P0171 Lean Bank 1 code. They will tell you to replace the O2 sensor that is reading the exhaust as lean and the computer is compensating past the expected limits. Therefore the PCM is telling you that the O2 is telling it about a lean issue. The lean issue probably exists and in the case of this code..you'd be replacing a perfecfty good sensor.

Wheel bearings..if they are bad.. get them fixed. It can be difficult to diagnose other noises when you know you have parts that need to be replaced.