Sorry, I am using an Arduino Nano. I just tried it on the d13 PIN (the one with the integrated LED) and I get a beautiful square wave output! The scope works! Tomorrow I'll get it hooked up to the tach output on the ECU and I'll see what we're going to get there!
https://photos.app.goo.gl/QT8PNQSviEZt5MmP6
https://photos.app.goo.gl/QT8PNQSviEZt5MmP6