This article presents the procedure for the ignition system wiring changes when swapping a 1991-1994 ECU into a 1990 car with a 90 wiring harness, gauges, and coil.
This procedure corrects the tach signal so your tach works with a 91-94 ECU. This procedure was covered on the KeyDiver web site which I give full credit for presenting the original wiring schematics.
The procedure has been removed from the site and this article is provided to replace it. There is another procedure used for the ECU swap ignition wiring but that way is much longer and requires many more parts.converting a 1990 to a 1991-1994 ECU systemFor this process the only part needed is a power transistor from a 1991-1994 2.0 engine (N/T or Turbo).The 1990 coil...