O2 sensor code p0152,p0155

i have a actron scanner and i got these 2 codes from it...one is 02 sensor heater circuit malfunction bank 2 sensor 1...the other is o2 sensor circuit high volts bank 2 sensor 1...my question is which of the 4 sensors i see coming off the motor is bank 2 sensor 1....i didnt think there where 4 sensors on the 4.0 but when i looked under there was? its a 2000 HO 4.0...thanks..