Hi I just got a 2003 Cavalier-Ecotec engine, first thing I noticed was the engine light came on, the rad fan stays on, and it stalled on my us. P0138 comes up, and I think i's for the O2 sensor after the converter-has anyone else run into this? If it is the rear sensor will the rad fan go off? I heard these two things are related-hope the stalling is too lol Thanks in advance

DTC P0138 HO2S Circuit High Voltage Bank 1 Sensor 2