right i've been playing with help from my dad. if we reverse the wires we get a peek the trough. he had a look at the pcb i have from the donor car, and one of the signal wires is earthed as soon as it gets to the oem ecu.
The signal is put through some diodes, zeners and resisters. to make what would resembe a sqaure ish wave, so i'm just guessing that it was pot luck that got them wired that way as it would seam to only use half of the wave.
this is the same for the 6 tooth signal, but i could not start the car with it unpluged. so only had pcb to look at.