swaps are not easy . many things there are that Suzuki never documented, at all.
good it has an RPM output pin, that is good news...
so that needs scoping first.
there are many ways to drive this pin (ECU side)
open drain or collector transistor. or? and with or with out internal pull up resistor.
a full totem-pole driver .(best)
it might have a series resistor on that pin too, but can be discovered easy with any scope even that china one (Pico brand like) 50v inputs peak not too bad beats 5v max.
The output can be 5v or or 12vdc and can be current limited at 1mA 10 or 100MA.
a2/a10 tacho out, here? 97. j18 sport.
https://fixkick.com/ECU/18L/18LiterECU1.pdf
What to do is use MOSFET or 2 in on the pin, to buffer that single to make 12vdc sqaure wave to the TACHO 97 stock
if the pin is open drain say then it looks dead, until you add say 510ohm resistor to 12vdc (ign. power ,key on power)
then connect that to tacho. direct, see if tacho works if not scope the pin under load, see you get 12vdc to 0v swings. if not we fix that first ask.
we do not know now the source impedance of the ECU tacho out pin nor input impedance of the tacho 97 but we will learn that easy as we go.
doing simple tests. using 1 scope and a box of test resistors for loads. (and the real connections too)
best i can tell is the tachometer must not have lower that 10,000 ohms impedance. (DC resistance same)
that makes for no greater loss of 12vdc square wave never blew 10vdc square wave.
this make this easy, from that view..
even 1mA drive can do that. 2k source impedance.
a scope tells the signals polarity
after seeing that tells use whether to use 1 or 2 buffers to make it work if direct fails. see? 1 is inversion ,2 is non inverting buffer home made. 0v is dwell time charge COIL so we make sure that polarity lands on the tacho pin, I would guess the tacho pin is 4x rate already but IDK, that, the scope does tall that,
voltage swing see.
see polarity
see pulse rate, all 3 at once.
good it has an RPM output pin, that is good news...
so that needs scoping first.
there are many ways to drive this pin (ECU side)
open drain or collector transistor. or? and with or with out internal pull up resistor.
a full totem-pole driver .(best)
it might have a series resistor on that pin too, but can be discovered easy with any scope even that china one (Pico brand like) 50v inputs peak not too bad beats 5v max.
The output can be 5v or or 12vdc and can be current limited at 1mA 10 or 100MA.
a2/a10 tacho out, here? 97. j18 sport.
https://fixkick.com/ECU/18L/18LiterECU1.pdf
What to do is use MOSFET or 2 in on the pin, to buffer that single to make 12vdc sqaure wave to the TACHO 97 stock
if the pin is open drain say then it looks dead, until you add say 510ohm resistor to 12vdc (ign. power ,key on power)
then connect that to tacho. direct, see if tacho works if not scope the pin under load, see you get 12vdc to 0v swings. if not we fix that first ask.
we do not know now the source impedance of the ECU tacho out pin nor input impedance of the tacho 97 but we will learn that easy as we go.
doing simple tests. using 1 scope and a box of test resistors for loads. (and the real connections too)
best i can tell is the tachometer must not have lower that 10,000 ohms impedance. (DC resistance same)
that makes for no greater loss of 12vdc square wave never blew 10vdc square wave.
this make this easy, from that view..
even 1mA drive can do that. 2k source impedance.
a scope tells the signals polarity
after seeing that tells use whether to use 1 or 2 buffers to make it work if direct fails. see? 1 is inversion ,2 is non inverting buffer home made. 0v is dwell time charge COIL so we make sure that polarity lands on the tacho pin, I would guess the tacho pin is 4x rate already but IDK, that, the scope does tall that,
voltage swing see.
see polarity
see pulse rate, all 3 at once.
http://www.fixkick.com