# Does your auto require a FOB to start?

Joined Jul 18, 2013
25,206
Had an instance where the FOB would not work to open the car or trunk due to dead FOB battery, Fortunately used the emergency door key to enter and when the FOB was placed in the console just started after some juggling.
Battery was at the end of its expected 3-4yrs life.
I carry spare CR2032 in my wallet now.

#### GetDeviceInfo

Joined Jun 7, 2009
2,095
Wife’s car needs it. Helped the neighbour who’s vehicle alarm started and wouldn’t shut off with the FOB. I disconnected the vehicle battery while she went and changed the battery in the FOB. Everything worked good after that.

#### shortbus

Joined Sep 30, 2009
9,372
I made the mistake of putting my fob in my back pocket after opening the door, car wouldn't start got a message on the screen that no fob was found. The thing will open the doors from over 30 feet but not go through my body. Car and fob was only a few months old at the time.

#### dl324

Joined Mar 30, 2015
14,458
My 2000 BMW won't start without a FOB. Fortunately, the key I normally use gets recharged when it's in the ignition switch. The other uses a primary battery (the battery is at least 11 years old and it still works).

#### cmartinez

Joined Jan 17, 2007
7,699
I made the mistake of putting my fob in my back pocket after opening the door, car wouldn't start got a message on the screen that no fob was found. The thing will open the doors from over 30 feet but not go through my body. Car and fob was only a few months old at the time.
Wow ... an RF blocking butt! ... that's like a superpower!

#### Ya’akov

Joined Jan 27, 2019
5,659
I made the mistake of putting my fob in my back pocket after opening the door, car wouldn't start got a message on the screen that no fob was found. The thing will open the doors from over 30 feet but not go through my body. Car and fob was only a few months old at the time.
RKE (Remote Keyless Entry) and RKI (Remote Keyless Ignition) use the same method with one important difference.

In RKE the car interrogates the fob and if it can receive the reply at all in decidable form it unlocks but in RKI then you press the ignition button the car interrogates the key and checks the RSSI of the response to make it so you can't start a car when the key is outside.

So, it is much easier to attenuate the RKI signal enough to make it fail than it is the RKE.

#### MrSalts

Joined Apr 2, 2020
1,762
Wow ... an RF blocking butt! ... that's like a superpower!
I have a Logitech wireless mouse with my laptop. If I have the usb dongle for the mouse plugged into the left USB port and put my left foot on the footrest to raise my knee, the RF is blocked by my leg. It doesn't take much.

#### crutschow

Joined Mar 14, 2008
29,785
I have a Jeep with a keyless entry/ignition.
If the FOB battery is dead you can enter the car by using the hidden key in the FOB.
You then push the Start button with the end of the FOB to start the car.
It apparently interrogates the FOB by some method that doesn't require the FOB to be powered (perhaps some sort of RFID?).

#### Ya’akov

Joined Jan 27, 2019
5,659
I have a Jeep with a keyless entry/ignition.
If the FOB battery is dead you can enter the car by using the hidden key in the FOB.
You then push the Start button with the end of the FOB to start the car.
It apparently interrogates the FOB by some method that doesn't require the FOB to be powered (perhaps some sort of RFID?).
It uses RFID. Many cars have a place to put the fob if the battery is dead marked on the steering column.

#### shortbus

Joined Sep 30, 2009
9,372
Wow ... an RF blocking butt! ... that's like a superpower!
That's less than I thought the post might get. I figured there would be something about a fat a.

#### killivolt

Joined Jan 10, 2010
829
I was a service writer for Pep Boys, lady came in one day subject of remotes and distance RF, the car is around 30ft away from the front door I needed to go back out and read the Vin and info on the vehicle she had locked it, she said not sure if I can unlock the door or not the battery is low, I said give it a try, didn’t work she said let me try this……… something she seen on “social media” stuck the remote facing toward the back of her mouth hit the button and unlocked the car.

Mind you, inside behind the glass door, 30ft away, I said no way.

I said point that thing and try again, no result, then again she stuck the remote back in her mouth facing toward the back of her mouth press the button and locked it again.

I did a test opening the door did work. But she kept moving forward from the door out about 5ft from the entrance, closer to her car in the parking lot. Still unsure what exactly had happened that day. Still makes no sense at all.

kv

#### nsaspook

Joined Aug 27, 2009
9,727