On a morning news cast the narrator showed that if you and fob leave your car, someone can jump in and drive off. So being the engineer curious, the wife and I tried an experiment. On our very quiet road I got out with her purse with fob and she drove off. At some point the car chirped no key detected. She drove and turned around without stopping and came back to house, stopped,, and thats all the car went. No more movement. Gave back purse, car was happy and wife put it into garage. So while this is probably old news, but still good to know how car would respond if fob battery died while driving and the warning popped up. I know that you can put fob on steering wheel some place(?) and it can be read. Does the software then remove the warning until you turn car off? Starting again would require placing fob on steering wheel or replacing battery.. Can't imagine trying to drive while holding fob against steering wheel with one hand
My fob for my 2011 Gen3 has gone through many batteries. On the second or third time, I experimented with it. The fob must touch the 'Push to start' button. But only on one specific corner of the fob, so I marked which corner it is. Since I did that, it is no longer such a big deal when the battery dies.
I don't think there is any part that specifically must 'touch' the start button. The little RFID chip contained inside the fob just has to be within range of the start button's RFID antenna.
Trollbait, interesting question. Does the fob even need the battery to keep car running? That is, is the fob just being pinged by the car antenna just like those store anti-theft tags? I know you need to hold fob near start button to start car but then do car antennas ping fob thereafter to insure fob is still in car? Battery would be used to send signal to car to open doors, car alarm etc. but is battery activating something in fob that does handshake with car software?
I would have definitely separated the fob from the purse… I’m not fully understanding; did the car continue to run, at least till shut down? That’s as expected.
My Prius ran after the fob was removed until powered off. Then it couldn’t be restarted until the fob was back. And you didn’t have to touch the fob to the power button, just hold it near when pushing it
The engine continued to run, but when wife completely stopped at driveway, car would not move until the fob was put back inside car. I was just unsure if Prime would continue to drive stop/go until shutdown, or as happened here, "fails to proceed" (Rolls-Royce def of a breakdown ) at first full stop. Would be useful to know if fob failed so you could at least pull off and stop rather than on roadway.
I just got done trying this in my gen 3, and what mine did matches what Mendel, bisco, and rjparker have posted. Once the triangle and "KEY NOT DETECTED" message came up, they stayed up, but nothing interfered with driving the car. There was an extra beep the first time I shifted from P, and the triangle flashed for the rest of the drive. But I came to full stops, shifted into P, shifted back out of P, and continued driving the car. Nothing was ever prevented as long as I kept it in READY. Of course, the OP here is driving a newer-gen Prime. Could the behavior have been changed for that generation? Maybe, but I may remain skeptical until there's more corroboration. In my gen 3, interestingly, I drove quite a distance after Faraday-shielding the key before the KEY NOT DETECTED message came up. In fact, it didn't come up until I parked somewhere and opened/closed the driver's door. It came up the instant I closed the door.
