Hi I am trying to replace a O2 sensor in a 1996 Sedan Deville. The Snap On scanner is giving a "Lazy O2 Sensor - Bank 1 Sensor #2" message. The local dealership is telling me that there is only one O2 sensor in this car. The local parts store has 3 options for replacement O2 sensors including upstream and downstream sensors. Any ideas? Thanks in advance. Jim