Chip or radio in modern car keys as part of anti-theft system?

OK. I understand the confusion.
Transponder key is the correct name instead of chip key.

The battery in your key fob is used to operate the buttons (unlock, trunk, lock). When you put that key into the ignition, that battery is not used at all for the “transponder” function, e.g. activating the RFID circuit with the car that says “this key is legit - ok to start car”.

If you only need a replacement transponder key (without the buttons for lock, unlock, trunk), you can get it at a dealer, locksmith or hardware/improvement store.

Several years ago the hardware/improvement stores all began advertising that they sell transponder keys and they can program them - for less than others. They can do that without the expensive equipment the dealer or locksmith uses because they transponder keys they sell have batteries in them.

I hope I was clear this time.

@JoeMario How does the addition of a battery allow them to register a new transponder key?

I don’t know the details.
When I was talking to a locksmith a few years ago that I know and trust, I asked about the new “transponder key” programming signs going up at various hardware/improvement stores.

Specifically I was curious why they were not in the business for years, and then suddenly all jumped in seemingly overnight.

The answer was a company made a system they could buy for far less than what the dealer/locksmiths use. That system uses transponder keys with batteries in them (used for the RFID functionality), whereas the ones you buy from the dealer/locksmiths do not.

No, not really, sorry. Here is my understanding.

I have an older (year and a half) key-fob that doesn’t automatically unlock the car doors and I need the mechanical key to start the car.

Newer cars have a key-fob (aka smart key) with the mechanical key hidden, only as a backup. The car searches for it’s presence and if it detects it (the key-fob sends a return signal), unlocks the doors. Then the car looks for a stronger signal which indicates the key-fob is near the dash and turns on the ignition and allows the user to push the start button.

I think you are saying that for case 2 above, there is no battery in the key-fob. From what I read, this is not true. But anyway, battery or not, the duplicate key, whether made by the dealer of by home depot) has to be made the same.

Of course, there are many versions, one for each manufacturer, and there probably are major differences.

I was only referring to the smart keys that have to be inserted into an ignition switch and turned to start the vehicle. I.E. the kind that if you want a new one, it needs to be cut from a blank, and programmed.

For example: See

The smart keys that “send a signal” enabling the user to simply press a button are different.

My apologies for any confusion.

Like I said before, with our Acura you can’t lock a purse with the key fob in it in the trunk anymore. It thinks you are locking yourself out. As discussed a few years ago though, my wife claims she was also locked inside for a minute or so. I haven’t really tested it but if you are inside W/WO the key fob I’m not sure, and the doors lock, either automatically or using another fob, she claims she could not open the doors. Every thing was dead. Unlock button didn’t work as well as inside door handle. There was a case of a guy dying inside his BMW when his friends locked him in to sleep it off. Might be worth a check anyway.

I think it’s safe to say that there are a number of different types of systems in current use. In my car, I can unlock the door with only a physically cut blank but it will not start the car, but if I have the old FOB hanging next to it on the key ring it will also start the car. I’ve done it, just to see if it would work.

It will automatically unlock the doors if you open them with the key in the ignition, and it will not allow me to lock them with the button if the key is in the ignition and the door is open. This is (I assume) to prevent someone from locking themselves out with the key still in the ignition. It will, however, allow me to lock and unlock the doors with a physically cut key (no chip) with the engine running. I do this to warm the car up on cold days when it’s been snowing and I want the defroster operational before driving away.

I’ve also run into other various systems that get downright weird. In some cars I think the car’s brain is on drugs…
And I have no doubt that as the kid-geniuses in the design department dream up new ways to program the BCMs it’ll get even weirder. Hopefully it won’t get as complicated to unlock the cars as it is to change some of the radio stations. :smiley:

It looks like you can get blank chip keys for my car for like $10 each. You take them and get them cut, then use a simple procedure to get the car to see them as one that is paired to your vehicle. You get 8 chances at pairing different keys so do not want to blow it by programming a poorly cut key. It sounds like you are more programming your car to see the key, rather than programming the key.

Most cars since the early 2000’s came with a valet key, and most of those aren’t susceptible to water. I use the valet key on my boat keyring (one of those floating ones) all the time. I can’t tell you how many times it’s started floating away after being dropped into the water. Even our new Camry has the little tiny key inside the master FOB. The FOB allows keyless entry (grabbing either front door) and exit (touching the outside of either front door handle) and trunk access (hit the open button from outside). As an aside, my wife loves it - she never has to look for the key anymore - it’s just buried in her purse somewhere. But, the little mechanical key can be used to lock the drivers door (with the others already locked). I haven’t verified the security system with it yet, though. I know it’s locked - but not sure about the alarm part (probably not). I’ll check that tonight. I don’t tow with it, so I never thought to see how it operated.

The cars that I’ve dealt with (Toyotas, some Chevys, Fords and Hyundais), programming the computer is exactly what you’re doing. You generally need a master key, and use that to program a slave key (or another master). This tends to be a problem if you lose both master keys, as you’re subjected to a car that won’t run at all (or only in “valet” mode), unless you replace the computer and keys at the same time. It’s a very expensive mistake. If you lose a master, make sure you get another master programmed soon.

My car requires TWO master keys to program another one. I guess this is so someone borrowing the car can’t make a copy as they are unlikely to have both keys. Since it only came with TWO keys to start with, I plan to make two more copies in case I were to lose one. It sounds like this is a big mess. I am sure the dealer could make another but am sure that would cost much more than buying a couple blanks, having them cut, and then programming the key.

There is a local locksmith I have used in the past who seems to do a good job. I bet he will have all of what I need on hand locally.