I have got a new o2 sensor for my front bank before cat. The o2 sensor on the car has 4 wires. Blue, White, Black, Black. Im guessing the black ones are the + and - to the heater. Im not sure however on which is the Signal and which is the Ground on the factory O2.. The O2 I purchased is a 4 wire, Grey, Black, White, White. I know all the locations of this harness..

If anyone knows which is Signal and Ground - Blue or White. Please Help.
Thanks.