What year is it? Check this out https://montecarloforum.com/m_12459/tm.htm , yours may qualify, mine did. Mine was throwing a po420 code, but I don't think it is absolutely neccessary, maybe it hasn't gotten bad enough yet to throw it.
I called GM direct about it and they got in touch with the dealership here. My vin# fell right in the middle of the bad ones.