I just purchased a '97 Jimmy with an engine light on at all times.I did a scan of the codes and came up with a 0140 (O2 Sensor Circuit No Activity Detected) and a 0719 (Torque Converter/Brake Switch B Circuit Low). Does anyone know what could be causing these faults? (I am assuming the first is simply the O2 sensor) Any help or suggestions would be appreciated. Thanks!