Have you verified that it is 1v square wave that the ECU, or are you using a data sheet. If you verified it - what did you use, a voltmeter or a scope?
dont really know much about transistors, i just experement or copy diagrams off the net and adapt to my needs, but I believe 0.7v will trigger a transistor, so mabey you could get away with a single transistor and mabey a few resistors - im sure someone who knows what there talking about will chime in with something useful.