2017 86 tach signal
 

Ok, let me put this in other words. From what I've searched so far, there are various places to get an RPM based pulse in a base model 86. I started at the ECM (and I have no desire to go back into can of worms
with my old eyes), and apparently the four locations on the bottom connector are all to ignition coils. They all go through the AC1 connector in the engine bay. Where is there a diagram of that connector? I've entered every set of search words I can think of.

Which connector? The plug at the coil pack has 3 wires. Brown w/white stripe is keyed 12vdc hot. Black w/white stripe is chassis ground. The 3rd is colored and is the ECM trigger, on pack 1 it is blue w/yellow stripe I believe on my 13'. You can test this by pulling the connector and probing for continuity. The one that has chassis ground is, well ground. Key on check which one has 12vdc. The other will be your trigger. Then correspond to the AC1 connector. The only AC1 pinout I could find was for a 15' but did not give wire colors.

Just what I needed, with a "why didn't I think of that?" thrown in.