Wiring a Lambda/O2 sensor...

[spoodler]

Can anyone please tell me how to check the wiring on a car with a four wire sensor? It's not the wiring on the sensor that I need to check but the wiring on the car. I know that one will be earth, one sensor and two heater. I have bought a new sensor but wish to confirm the wiring before fitting (rather than just replace like for like) as I think the previous owner wired a replacement sensor incorrectly.
Haynes type manuals aren't available and wiring diagrams/colour coding available on the 'net contradict each other.
Thanks.

[E-bmw]

Surely, if you are fitting the correct sensor, you just plug it in and you can't get it wrong.

If you want to use a "universal sensor", (quite frankly, I wouldn't bother, you WILL be changing it every year) then you just need to follow the wiring diagram wrt the instructions on the new one.

[spoodler]

Thanks for the reply.
The previous owner had fitted cheap replacement sensors by splicing into the loom, therefore I can't just plug in my nice shiny new one. The actual connecting of the sensor/making up a plug isn't a problem but I need to confirm which wire is which before I damage my expensive new one...
The earth should be easy enough to work out. Can anybody advise how to tell the heater wires from the sensor wire please?
Thanks.

[AceOfHearts]

In my car the Lambda heaters go through a fuse, so if you know what fuse it is you can buzz the cable out with a meter that way?

[eliot]

I would expect to see two grounds and a swiched live, the remaining one being the sense.

[E-bmw]

^^^^^ Wot 'e said.

[DVandrews]

Generally the two wires that serve the heater carry a higher current so they are beefier then the supply and sense wires and will be a single colour. Again generally, the 12v supply will be a single colour and the sense will be a two coloured wire.

Dave

[Jimmyarm]

What car & engine code ?

If you can find out the pin out data for the ECU that will give you the colours (as you can look at them on the plug )

[Fullmel]

If you have a 4 wire sensor, the heater part of the sensor will be the two wires that are the same colour.
Then you can work out the other two.