Originally Posted by
norfy
to confirm, you have the correct wire for the tacho from the nissan side.
is it a straightcam sr20? just thinking the earlier s13 engines/tacho sr/ca use a negative pulse tacho signal (negative-off), whereas the later sr20 as fitted to s14/a use and alternating pulse (negative-5v). We usually have issues getting the tacho to work when fitting a later sr20 into a s13. In this case you need to fit a 33k pull up resistor to the blue/black wire on the ecu connector.
im thinking, if youve got an earlier straight cam and the bmw tacho needs a negative-12v pulse then youll need to fit a pull up resistor to get that. You could quite easily fit that to your pcb.
just a thought, and its something to check