An accidental keyfob discovery

I learn a lot of stuff that is not obviously “useful”.
I learned something “new” and useful today: a keyfob with a dead battery or no battery, will still start my car.

The car keyfob I had been using - failed, due to the battery.
Therefore, I switched to the “other” keyfob.

I took the old battery out of the non-functional keyfob. That was… 6+ months ago. Or longer? I don’t really remember.

Recently, I picked up the fob WITHOUT a battery, by mistake, and left the house for an errand.

(Forgetting there was NO battery in the fob.)

I had to touch the “start” button with the keyfob, to start the car. The fob did not operate the door locks etc.
I realized I had the “dead battery” fob, but just went on with the errand - no big deal.

I used the manual key thing, while out on the errand, and just touched the fob to the Start button to start the car.
I figured the battery was just too weak to operate the start button from a meter away.

A few months ago, I had picked up a couple new 2032’s and, today, got around to inserting one into the fob that did NOT have a battery.
When I opened the fob… no battery!

I remembered that that fob HAD STARTED THE CAR…
I took the fob (sans battery) to the car and verified that touching the fob (sans battery) would indeed start the car.

I’ve owned Toyota hybrids for 13 years. I never knew that the fob - sans battery - would start the car.

In the past, I’ve fretted that a dead fob battery would strand me. Now, that stressor is mute.



I’ll bet that’s even in the owner’s manual. At least it is for DW’s Subaru Outback…

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in several GM products with only a fob to start, there is a special compartment that allows the car to energize the circuit. This is available in a special compartment adjacent to the glove box.…

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I don’t know about other brands, but I have had several Toyota’s and what you describe is in the manuals. The FOB actually has a seperate RFID circuit (like in a security card) that responds when right next to the start button. This is designed to be used exactly like you used it…dead or missing battery.