Can anyone please help me get the wiring right for the front lambda sensor on my 2005 wrx.

My new sensor (from a hawk sti, i think) has the same colour wires as my old one (2 black, 1 blue and 1 white) but the plug is a slightly different shape so i have wired it into the old plug but i can't get it to work. Keeps throwing cel for o2 sensor.

The connections on the car's plug are 1 black, 1 black with red stripe, 1 white and 1 yellow.

I've tried a few combinations but i can't figure out what wires to connect.

 

not a good idea swap round the wires..one circuit is 12v and the other is low voltage signal. putting the 12v into the signal circuit may well damage the ecu and the sensor.

 

Oh dear. Thats not what i wanted to hear.
I wired it all up the same as the previous sensor to start with but when that didn't work i tried
black-black/red
black-black
white-white
blue-yellow
as that seemed the most logical. but no joy.
I hate electrics.

 

I am pretty certain i have it wired up correctly know but its still throwing a CEL.
Sorry if its a stupid question but can anyone tell me how i can check if i have damaged the ecu wiring or if the sensor is knackered?

 

Checked the voltages at the plug and got this:
From ecu
black/red = 2.7v
yellow = 11.9v
they must be heater gnd and +ve
white = 3.8v
black = 3.8v
signal wires for ecu

The signal wire from the sensor reads a constant 3.8v when the engine is running at cold or warm idle. I take it that means its knackered?