I have 3 OEM key fobs from Lexus with new batteries. I have tried using different keys and the issues persists. I do have a relatively new 12v battery.

While I'm sitting in the driver seat (engine running) with my keys clipped to my belt loop I get the dash alert "Key Not Detected" on occasion when a passenger exists the vehicle and closes their door. The alert will literally remain on the dash while I'm driving for a long time and abruptly turn off or it'll go away if I power cycle the ignition.

Typically my cell phone is in the opposite front pocket or it's just laying on the center console. There's nothing around my keys that I would believe to be causing some sort of interference.

This doesn't happen every time, but it's been happening more frequently. I have no idea what's causing this. I brought this up to the attention of my local dealership and they don't have an idea either. They want to charge me a ton of hours for diagnostics that I'm just not confident will solve anything.

Does anyone have suggestions on what I could potentially do for this issue?

 

This happens fairly frequently to me, but I attribute it more to what else may be in my pocket at the same time and/or the temptation of cheap Amazon batteries that should be nice and fresh, measure 3.3V, but don't last at all. There's no guarantee that your dealer is spending on good batteries, either...the amount of aftermarket parts I see behind my dealer's parts counter shocks me. I'll usually get lots of key messages about 3 weeks before I get the low battery warning.

De-tuning of the antenna from pocket contents is another culprit, but you've indicated that you're pretty good about that. If it bugs you, take your key out and hold it up to the power button, it should go away.

Going forth, I now spend the money on name brand, recently stocked batteries that I pick with my own hand..as ridiculous as the pricing is.

 

I've tested the batteries that I purchased on my own. It came up at 3V according to my meter. I've tried waving my keys around or holding them against the Push to Start button with no success.

This is an issue because not only does the car have audible alerts, it has a permanent flashing warning icon on the dash while I'm driving. It's very distracting. The text alert also displays over the LCD screen on the dash which prevents me from using that display. Of course I can cycle the display, but after a few minutes it goes back to the warning screen.

 

There was a period after the Tsunami in 2011 that the key fobs supplier was unable to provide enough (any?) fobs.
Lexus sourced from another until things got straightened out. We noticed at the Dealership during our usual task of
moving cars to plow the snow that we were getting quite a few "key fob not detected" messages. Turned out that the
substitute fobs were doing the interference. When we tossed all the new car key fobs in the box as usual it seems
that the newbies were jamming the signals.
MonkeyWren - as two fobs are standard and you have three, perhaps the third fob is from the other supplier (I never
knew the name).

 

It's possible. However, I've tried all 3 key fobs. Maybe I'll try another pair of fresh batteries or a different brand as someone mentioned above.

I just took out the battery from my fob. It came up as 2.97V. The newer battery I just put in is 3.32V. I also switched fobs.

 

No dice. I'm still receiving the error with new batteries and a different fob.

However, the alert goes away after about 3 to 5 minutes of driving. The alert starts as soon as the passenger exits the vehicle and closes the door.

 

For whatever reason, halfway through my night of driving the error messages for the key fob not being detected went away. I don't know what to make if it.

 

So, I instrumented up one of my 'good' batteries, which reads 3V at rest. Under load (pushing a button or being commanded by the car), it dips to 2.7V, which is essentially dead. This battery was 'new' 3 weeks ago. Bought a new energizer and it doesn't dip as much.

Another thing to consider; we both live in climates that spread salt on the roads. With antennas all around the car, it's not entirely far-fetched that in wet/salty conditions, the antennas are getting de-sensed. Couple that with how much of a salt layer is on your car between washes....

 

This happens randomly to me also in my 2014. Brand new battery, key fob on the console. It's mildly annoying.

 

My issue got better when I tried a different brand battery. It seems it's not related to the car itself.

 

Congratulations! It seems like the issue was caused by the battery. Are you still experiencing the same problem now?

 

It seems the key fob eats batteries pretty quickly. I am experiencing the issue again, but I haven't changed the batteries in a little while. It looks like I'll just have to live with this. I'll change the batteries more often now.

 

Not sure how close your fob is to the car at home, if it close, there's a constant communication so to extend battery life, put it in a Faraday pouch, they are cheap on Amazon.

 

My keys are at least 100' from the car. It's parked outside on the street. The spares are even further away. The house is old style brickwork too.