I had some weird things going on with my car this morning that I ignored and got stuck by the side of the road as a result.

When I first started the car this morning it was about 17° and it seems sluggish to start. I've got an 8 month old red top optima battery, the alternator is less than a year old, so that was weird in itself. It has always started strong with that Optima. I drove for a few errands stopping and starting car. After restarting, when putting it in drive or reverse the gas pedal would not input any response. I push the pedal all the way to the floor and the Revs stayed at 1500/idle. In park and neutral it would rev freely. Happened once - I turned the car off restarted it and it was fine. Happened again 10 minutes later in my neighborhood and I pulled over to the side of the road, Shut ut off, try to turn on again and my battery is dead. Tried jumping it off my wife's car and it seems the battery is now completely dead.
I've never had my g leave me stranded. Wondering WTF happened? Possible Battery issue #1, but the dead pedal in drive/reverse? Anybody had this experience? Is low voltage causing the drive-by-wire system problems?

I Necro'd a thread from 2011 in 'Engine' forum, OP had same issue, there wasn't any follow up on a fix.

Towed it to the shop (the same one I was at this morning looking at my still leaking pinion shaft). They are going to diagnose and re-repair pinion seal.

While I was sitting by the side of the road I had enough power to scan the ECU with my OBD and there were no faults.
Another thing I almost forgot to add was when I had the car in drive it still showed N on dash indicator instead of D.

 

Turns out it was the alternator. Had it replaced just 27k miles ago, about 13 months on it. Car is back to normal after alternator/battery charge.

 

Was it replaced under warranty? Or did you have to pay out of pocket again for another alternator? It's best to stick with the oem alternator.