my engine light is back on, Just had it fix only had the car less than one month on 2007 Suzuki Reno

the technician told me I need to have the Oxygen sensor repair. I had the castylic converter replace the transmission senor replace and trans flushed. Would me needing an Oxygen sensor causing the engine light to come back on. the car shift just alittle rought when I park it into the garage. it has 133,000 miles on it only had the car since aug 2010.last repair 2/12/13 11ISZ: diagnostic

Asked by for the 2007 Suzuki Reno
any sensor malfunction or wiring will cause ck eng light to come on.why did you repl catt?