Car Key reprogramming and transponder instructions
The cars that are being made today are being fitted with various types of security devices, which will help prevent the theft of motors.
The security device that we are talking about is key coding.
This is where a transponder is fitted to the key, which in turn will be recognized by the vehicles ECU; this will then allow the car to start. If the key is not recognized the car will not start and on some vehicles the engine management light will continue flashing, on other vehicles the car may start and then cut off.
Here are free instructions for various makes of cars to reprogram your chipped key
Audi, BMW, Citroen, Fiat, Ford, Jaguar, Land Rover, Nissan, Peugeot, Porsche, Renault, Rover, Seat, Skoda, Subaru, Vauxhall, Volkswagen
Different types of keys
Most modern car keys are 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 also be expensive and time-consuming to replace if lost or broken.
Electronic, coded transponder chips embedded in the plastic body of the key were introduced from 1995. The chip is passive, so it doesn’t need a battery – 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 if/when you obtain a new key with a new key code.
Many early cars were supplied with a ‘master key’ (often red), which was not intended for normal use. The dealer uses the master key to programme a new or replacement key for the car.
Unfortunately, if you damage or lose the master key it could cost hundreds of pounds to replace. You may have to replace the complete engine management system costing more than £1,000.
Car manufacturers have virtually stopped using master keys. They now hold car-specific security information in a central database, which the dealer uses when reprogramming the car and a replacement key.
If you’re buying a used car, check the handbook. Make sure you get all the keys including a master key if one was supplied when new.
Very early transponders used ‘fixed codes’ – the key sends the same coded signal every time it’s used.
Keys with ‘rolling codes’, which means the transponder code changes every time the key is used, were introduced from 1999 and are now very common.
These should be virtually impossible to copy. They offer improved security but they’re even more expensive to replace if lost.
Virtually all new cars are supplied with a remote control to unlock the doors and turn off the alarm. This is very convenient, but not without its problems.
Some use infrared but most 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 MoD communication, radio amateurs and other common applications. Interference can occur and in the worst cases the car can’t be unlocked.
Modern cars are much less likely to suffer from radio interference but the problem remains for older cars, particularly those built before 1995.
What if the remote control doesn’t work?
- Check that the battery in the key isn’t flat.
- If you suspect radio interference try using the remote control close to your vehicle.
- In extreme cases, move 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 should be explained in the handbook but the handbook will probably be locked in the car when the remote fails – familiarise yourself with the procedure now.