2003 GMC Yukon

Engine Mechanical problem
2003 GMC Yukon V8 All Wheel Drive Automatic 90,000 miles

My vehicle failed emissions because of a 02 sensor. The fault code was po161 which was a 02 sensor heater circuit malfunction(Bank2 sensor2). The tech told me change this out. He stated that this was the downstream 02 sensor before the converter. My question is I have two converters. I replaced the one on the passengers side. This made the engine light go out. The vehicle still idles really low like it wants to shut off. There arent any warning lights on now. Should I change the other down stream 02 sensor? Does this sensor affect air and fuel mixture?
March 9, 2009.

Hello, if you two o2 sensors in each bank, then bank two sensor two is after the cat, passenger side. I wouldn't change aything else, if the codes are gone.

I always thought the sensor after the cat just monitored the cat efficiency, other than setting a code, I didn't think the computer would react? I have seen conflicting info on this point.

Mar 9, 2009.