Originally Posted by Bald Paul

"Back in the day" you could get your car running with a matchbook cover to gap the points, and some basic tools to adjust your derailleurs.

I was a regional technical specialist for an import car manufacturer for about 30 years, after spending 10 years before that as an ASE certified master tech at dealerships. Here's a little advice for you. If your modern car stops running on the road, call a tow truck, because your chances of lifting the hood to see what's wrong are slim and none without very specialized equipment.

If your Di2 system develops some serious issue, you may need the SM-PCE02 PC Interface Diagnostics Tool (about $270, if you can actually find one) and a computer, which I doubt you'll have with you in your under seat tool bag. If you have an SRAM e-tap system, hope you're in an area with good cellphone coverage so you can use the app, and hope it's not a BT communications issue, or you're stuck.

If you drive a car from the 60s, or ride a bike with downtube shift levers, you're probably okay. Anything modern, not necessarily so.