Chk Engn Lght

I gotta 97 grand am with the 2.4 dohc engine, and for about a month the check engine light has been on - i took it to autozone to get the computer read and it came up with a "catalyst out of threshold" message. THe guy there suggested a bad o2 sensor, and the car has showed no signs of bad performance at all, so im thinking its somthing stupid like a sensor somewhere - any suggestions would be appreciated

First, can you give us the code number..this is important for proper diagnosis.

Before you change any parts, lets do some diagnosis

the code was a p0420 - catalyst system efficiency out of threshold

The diagnostics for that is pretty straight foreward...replace the converter.
What has happened is the converter has loss its efficency and is unable to do its job.
Now if for some reason you have less than 8 years or 80000 miles on your car, this repair is covered under your GM emissions warranty and would be repaired at no charge to you..

well thanx for the reply - the light went out by itself acually, prolly by coincidence but its really wierd - last night i realized my horn didnt work so i went to check the fuse for it, and it wasnt blown. so after i put the fuse back in when i started the car like 5 mins later the horn worked and the light wasnt on, so i think maybe it could be a short somewhere, but everythings fine now...i dunno