(G) Car broken into, kind of....

As I understand it, when the keyless entry is switched on, grasping the doorhandle triggers the car to send a short-range interrogation signal to the key fob, which responds by sending an "unlock" code. The theft devices amplify the car's signal so that the key can receive it several metres away. The theft device has a sensitive receiver, which detects the code from the key and transmits it back to the car, causing it to unlock.

If keyless entry is disabled, there is no reason for the car to send the interrogation signal so the key fob will not respond.

Using the button on the fob to lock the car should be secure as any device that "captures" that signal will probably be unable to replicate a valid "unlock" code, due to the code changing each time in a sequence only known to the locking system for your car. At least, I think that's how it all works!

Thieves have used jamming devices on remote locking systems which prevent the fob from locking the car as you leave it. However, you can tell if it has locked easily enough by ear and the hazards flashing.
I had assumed (apparently incorrectly) that to start the car, the system used something more sophisticated than signal strength. My 500X won't start if I hold the fob even a couple of inches outside the window, so I thought it may use a network of sensors in the car to determine the keyfob location by triangulation - that's what I would have done.

It would be nice if someone who really knew how these locking systems worked could give us an accurate description/explanation.

If keyless entry is set to off then I also believe that the car does not send an interrogation to the key fob. This has to be/must be a three factor/stage event - i.e. manual/physical initiated(1) request (2) and response (3) . If (1) was missing the car would self unlocking/lock when you do not want it to.

With regards to the key fob buttons then the car is permanently listening for correct code from the fob. And yes these are now rolling codes so each code is different.

The other day my fob stop working and I could not lock/unlock the car. No battery warning.. I tried my spare and mysteriously that did not work either.

After a few more tries with the main key it started to work again as did the spare.

I can only assume that in my tight jeans the fob button got pressed many times out of reach of the car and this caused the key fob code sequence to "march" on and get completely out of step with the car.

The marching code algorithms allow for missed (one or more) sequences but many missed steps can throw them. It then takes more lock/unlock sequences for the parties to get back in sync.

As for my spare not working then I guess both keys were on the same "seed" from being manufactured so when one key got out of sync so did the other. Two keys bought at different times would probably not have the same issue.

Puzzled me at the time as I thought that a more serious failure in the car security system had happened.

Is it worth worrying about this? That’s why I have car insurance...

Probably not worth losing sleep over with a 500X, unlikely to be stolen to order. Even if covered by insurance though, it's a shedload of hassle and inconvenience if your car is stolen.

Well for information to all my 500X display a message on the dash that the key fob battery was low (along with pretty colour picture).

On replacing the battery I noticed the following:

1) Circuit board manufactured by Continental
2) Just the one main chip with a pretty large coil assembly all around the chip

A little research and we see:

http://continental-carkey.com/

https://www.continental-automotive.c...ontrol-Systems

https://www.continental-automotive.c...mfort-Security

https://www.continental-automotive.c...mote-Cloud-key

Enjoy

I am a radio amateur and operate radios on HF, VHF and UHF. My wife and I have had a few Fiats, Grande Punto, Punto Evo and now have a Panda 4x4 and the 500x (keyless doors and ignition). All of these cars have issues with locking & unlocking when I use my UHF radios on 430 to 440 MHz. I have also noticed the 500x will not start if my transmitter is on. Once started it is fine. I've even stopped (accidentally) someone locking their 500 down the road. Power from the transmitter does not need to be high but is depends on proximity and power level. Manufacturers are allowed to use low power devices (e.g. electronic keys) in the ISM (Industrial, Scientific & Medical) part of the amateur band which is ultimately controlled by the MOD as they are the primary user. ISM users have to accept undue interference from other users of the band.

I've also noticed owners of some Fords unable to lock their cars if I am transmitting

Hi
I bet your popular!
I would not be happy with you living down the road from me, I'm surprised you have not had people bang on your door
LUIGI

Other than our own cars i've only noticed the problem with a 500 down the road. We have all sorts of makes and models by us and haven't noticed anyone else with a problem. Well I know it is not a fault with the radio as it happens with hand held, mobile and base units. I've been licensed for over 30 years and been on committees at national level on EMC issues. These types of problems have been around for years, at least i don't live next to a Fiat dealer.

Hi
Never the less.......some poor bugger goes to there unlocked car which they know they locked, and had stuff pinched out of it or worse....and it's ok by you, is that what your saying?
I don't care how may years you have been doing this...it's not right.
Theft from a insured car or worse' 'unlocked'' in void.
Like I said...good job you don't live near me with all that going on
LUIGI

No it's not OK but this problem has been around for years with electronic keys and alarm systems unfortunately. Any manufacturer using devices in the ISM bands have to accept the fact they are not the mains users of those bands and they may have problems (this is in national guidelines for frequency allocation). I have just checked the owners hand book and they have a warning on page 17, "The operation of the recognition system depends on various factors, such as, for example, any electromagnetic wave interference from external sources..."

The only reason I have mentioned this in this thread is to highlight peoples awareness to the problem that happens with many manufactures.

Not wanting to add/inflame this issue but I'm with G1KEA on this.

The salient points being multiple parties legally use the same frequency band and frequencies.

For the frequencies/applications in question then we are talking predominantly "near communications". I was astounded to find that my 500X car can be unlocked via the fob from 100m away. Even 10m would IMHO not be a suitable design. With such sensitivity in the locking system then it is going to be upset by any legitimate user of the frequency band.

The problem is over sensitivity of some systems that should be far less sensitive for the correct and expected operation. Taking this to the extreme would any car owner be happy if their key fob button got pressed (in the pocket) when they were a mile away from the car and the car unlocked?

In any such interference cases OFCOM can and do investigate and will check/identify the possible source. If all is found OK they can/do check the complainant's equipment for possible faults. An oversensitive, poorly discriminating, etc. system will leave the complainant at fault.