Just trying to power up my old stream as I think I may have found the code. I don't want to dismantle the car to try it. Have tried the - and + but guessing I need a third wire. Can anyone help?

Try a earth wire

You need to provide power to the anti-thief circuit as well as the head unit.

 

Have a look at the label, 12v to both safe and +UB and 0v to the one labeled with a ground symbol.

Cheers buddy