I', planning on installing a nav unit into my 90 fastback. I was wondering if anyone had a layout of the ECU for the 90 fastback.

 

Why do you need the ECU layout? All you should need is standard radio wiring layout. Or is this the kind that has performance meters built into it?

 

the nav requires me to tap into the spped snesor wire. so i need to know where that wire is in the ECU

 

Moved to the "Audio/Video" section.

 

Just splice it from the sensor. Or follow it up into the car and do it from there. There's a sticky in the drivetrain that has how to remove the 5th gear limiter....and it'll say which sensor is the speed sensor, just use that and follow the wire up.