"Key Not Detected" when someone gets into or out of the car in Ready mode

Ignore the lack of the cargo light being turned on. Recheck that the hatch is securely closed anyway.

If everything made sense in the first place, that wouldn't be the warning message for a loose hatch.

 

if you're getting a beer, check the 12v health

 

What about the dark red wine people ?

 

in what way?

 

why are you more concerned that it started about a month ago?

 

Have you checked your 12V yet? Try another battery in your fob. Is there any damage to your fob (dropped it)? Can you try a second fob? Make sure you're familiar with getting into the car with the mechanical key and starting with a dead fob (place the fob over the power button) in case you get locked out.

 

Even though you replaced it...I would try another fob battery. Sometimes you can get a "bad" new battery, or one that has sat on a shelf a long time.
Cheapest, easiest first step. Might not be the answer but it could be, and it's a cheap easy investment. Worst case? Issue NOT solved but you for sure know it isn't the fob. Best case? It works and mystery solved.

 

My 2010 did that several times on the way to church last week, My wife's key fob was in her purse as always. First time in 8 years and hasn't done it since.

 

Solution to “key not detected” when door is opened for passenger to get in or out of my Prius. (New battery didn’t help.)
Keep key fob away from other key fobs, credit cards.
My 2019 & 2012 Prius both had this problem, the “key not detected” message would appear and keep appearing every 30 seconds, while driving rideshare. Some days no problem until I got out and restarted later. 1) I moved 2012 key fob to left pocket, 2019 key fob in right pocket, separating the fobs. I tried letting the key fob hang out of my pocket. Still had problems.
2) Placed key fob on console (where Qi Charger would be); no problems at all.
3) I use small credit card wallets in both front pockets... removed credit cards from pocket with key fob, the problem went away. Returned old magnetic strip cards to pocket, no errors. Returned chip (& tap to pay) cards to pocket, errors again. This testing was conducted without restarting the vehicle, and did not differentiate between holding the brake in drive, or putting the car in park before the door was opened.
4) Replaced credit card cases with RFID blocking cases, no “key not detected” errors for weeks. Just for grins, I placed one chip card in an outer (no RFID Blocking) part of the card case, got the error.
Sorry for the long post, but this has been driving me nuts for over a year. In fact, I pulled the door switches on my 2012 Prius and disconnected the wires on everything but the drivers door, just to make the problem go away. I have now reconnected the wires and the same fix works on the 2012 Prius.
Bottom line:
Cloak all RFID items like credit cards, security passes, etc... and if you have multiple key fobs for different vehicles, separate them by at least eight inches.

 

finally, thank you!

 

Incredible discovery/fix! when I drive to scenic areas to go for a long run, my checking card w tap to pay is in my arm band. When I throw my armband near the 12
Volt socket next to heated seat buttons after the run and driv back, I get the same key not detected issue. But when my wallet is there, no issues. I realized long ago, I bought this wallet because it has RFID blocking capability

 

This happened to me yesterday. I didn't have my key fob near other fobs or my wallet. My 2010 was in accessory mode, and all of the doors were closed once I got in and sat down (I was cleaning snow from the windshield real fast).

My 12v was recently replaced, so I'm not sure if that's part of it. Since then I've also had my radio randomly turn music volume down on its own.

I'm going to take her in tomorrow and see what's up. I'll let y'all know how it goes.

 

Alright, the shop ran every code diagnostic available trying to find the issue. Everything came back perfectly fine without errors.

We tried to replicate the issue using the advice here, but we were not able to. The steps we took were putting my wallet (with RFID cards) in the same pocket as the fob. Nothing. We tried the cards directly on the fob. Nothing. We tried two fobs. We tried two fobs and the cards together. Nothing triggered the error again. So currently, we're still stumped.