h i, on the green/black ( gr/blk) wire with the connector disconnected ,what is the voltage reading at that wire with the key on ?
this same wire also, goes to the TPS sensor,the o2 sensors,the iat sensor and the egr .
see if the voltage reading is the same at each sensor.
It should read 5 volts .you may have to disconnect each sensor .
if the reading is still 12 volts ,this could be a shorted o2 sensor.
what I would do is this
disconnect the coolant sensor/egr/tps and iat sensors then see what the voltage reading is on the gr/blk wire
if it is still 12 volts then disconnect the o2 sensors one at a time and see what you have then .
if then the voltage goes to 5 volts then one of the o2 sensors is bad .
what kind of scanner are you using ?......jazzmaster ..