Everything you need to know about car keys

What to do if the remote fails, or you lose your keys

Lost keys are one of the top 10 causes of breakdowns.

Keys are the weakest link in the car security chain and you should look after them as you do cash or jewellery.

Insurance claims data shows common ways that keys are taken:

  • Stolen while the owners were asleep at night.
  • Stolen while owners have been in the garden or have 'popped out for five minutes'.
  • Keys left hanging in house front door locks.
  • 'Fished' through the letterbox or through an open window.
  • Stolen from workplaces, gym lockers and changing rooms.
  • Quietly picked out of unwatched bags or pockets in pubs and restaurants.
  • Taken following comprehensive burglary of the home – with the family car used as a getaway vehicle.
  • Stolen by way of threats, muggings or car-jacking.


If you need a new car key, for whatever reason,
call AA Key Assist on 03300 530 407

Three keys in one

Most car keys are actually three keys in one.

  • A mechanical key to release the steering lock.
  • A coded 'electronic transponder chip' read by the car when the key is inserted into the ignition.
  • A remote control to unlock doors and turn off the alarm.

These keys are secure but can be expensive and time-consuming to replace if lost or broken.

AA Key Assist can help if you need a replacement car key.

For greater convenience, many cars have done away with the mechanical key altogether and offer remote keyless entry and remote keyless ignition.

All you have to do is have the ‘key’ in close proximity in a pocket or bag and the car uses sensors to automatically ‘talk’ to the key.

  • Cars with keyless entry may be more vulnerable to theft.
  • Gangs have been known to follow the owner and use an electronic device to extend the range of the key so an accomplice near the car can use another electronic device to receive the signal and unlock the vehicle.

If you're concerned that your car may be at risk, you can protect it by keeping your key in a radio frequency blocking (RFID secure) pouch or wallet.

Transponder keys

Electronic, coded ‘transponder’ chips embedded in the plastic body of the key were introduced in 1995.

  • The chip is passive, so it doesn't need a battery, and the code is read when you turn the key in the ignition.
  • If the transponder chip is broken or missing, the engine won't start and the immobiliser's control unit will have to be reprogrammed when you get a new key.

Remote controls

Some use infrared but most remote controls use a radio transmitter to send a coded signal to a receiver on the car.

  • The operating frequency (418Mhz or 433.92Mhz) is close to those used by some communications networks, radio amateurs and other common applications.
  • Interference can sometimes occur, preventing you from unlocking the car.
  • Modern cars are less likely to suffer from radio interference but the problem remains for older cars, particularly those built before 1995.

Car thieves may also exploit this issue by using a jammer – a radio transmitter – to block the signal from your remote control when you try to lock your car. Always check your car’s locked rather than assuming the button worked.

If the remote doesn't work

  • Check that the battery in the key isn't flat.
  • If you suspect radio interference, try using the remote control closer to your vehicle.
  • In extreme cases, AA patrols have towed cars away from interference, so the remote can work.
  • Cars with remote central locking should have a bypass system using the normal metal key to unlock the doors without setting the alarm off. This 'auxiliary entry' system will be explained in your handbook.

17 February 2017

AA Key Assist

Lost or stolen car keys? We’ll get it sorted in a jiffy with our mobile key replacement service – call 03300 530 407. We can come out to you between 7am and 10pm, 7 days a week.