2003 CE Mirage Auto 1.5L tacho install journey summary
Purchase correct tacho (#4) by accident. Realise screws are missing. Fill in missing screws with ones from tacho-less old cluster.
Pretty much plug and play as the connectors had all the correct wiring. Oh wait, bouncing needle!! (Til this day I have no clue where the factory tacho signal came from) (white wire, wasn't any white wire on the ECU))
Try correcting grounds/earth together. Doesn't fix issue.
Revert and go for a drive. Cluster guages die. PCB twas cracked. Scraped plastic off over hairline crack and soldered to bridge the crack.
Cluster works again but still got bouncing needle. Need to use a different signal for tacho signal. Between rpm/tacho pin and pin 89 (crankshaft pin). As the tacho pin doesnt have any wires, crankshaft pin it is. Splice into it. Disconnect the original wire.
(PS the method for removing pins/wires from the cluster connector terminals is push with a thin object perpendicular to the pin against the lip in between the wire (see drawing (was found after destroying and cutting factory wire)). Or just cut the white wire and tape off.
Anyways splice into pin 89 to tacho signal worked wonders. Accurate and no bouncing needle! (And I can tune idle accurately now!)
So it seems later year mirages came with heaps of factory wiring for add ons (such as fog lights, power mirrors, tacho (the ground was present and good (obviously I needed to change tacho sig) but YMMV))
Now onto replacing door lock actuactors... (Done!)