Yesterday I learned that when my 2001 Ford Mustang is running, the key fob is disabled and will not let you lock or more importantly unlock the car doors. I started up the car in order to warm up the cabin, took the key fob off my keyring, and then locked the door behind me. I was only going to be a few car lengths away from it but I didn’t want anyone hopping in it and stealing it. This turned out to be a huge mistake. One call to AAA and 45 minutes of car idling later, they showed up to jimmy a door open for me so I could turn it off.
Interestingly my dad’s Ford Explorer, which is only a few years newer than my car and shares many common Ford parts, doesn’t do the same thing. It’s key fob works perfectly fine with the engine running. Hmm.