My sister-in-law'* 01 GA is throwing this code:

P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1

Would that be the sensor before the cat? Autozone wouldn't tell my father in law which it meant, but gave the price for a rear and a front sensor, bless their hearts...

My roommate has a GA and says that it is the front O2 sensor, on the manifold.