Guide
Car Key Fob Replacement or Repair: Which Do You Need?
A car key fob that has stopped working often needs a new battery, a new case or reprogramming rather than a whole new key. Try the battery first, then ask an auto locksmith to test it. A full replacement, cut and programmed, costs about £100 to £282, from WhoCanFixMyCar booking data and StageMyCar.
Does a car key fob that stops working need replacing?
Not always. Most fob faults fall into one of four kinds, and only one of them needs a new key:
- A flat battery. The buttons stop working or only work close to the car. The car may still start, because many immobiliser chips work without the battery. - A broken case. Split shells, worn buttons and snapped blades are common. The electronics inside are often fine. - Lost programming. The fob has dropped out of sync with the car, sometimes after a battery change or a repair. - A failed circuit board, from water, a fall or age. This is the case where a new key is the answer.
An auto locksmith can test which one it is in a few minutes, so ask for a diagnosis before you buy anything.
Can you change a car key fob battery yourself?
Usually, yes. The car's handbook shows how the case opens and which battery it takes, and the battery is a standard coin cell sold in most supermarkets. Note which way round the old one sat before you take it out.
If the fob still does not work after a fresh battery, stop there. Some cars need the fob to be re-synced afterwards, and the handbook says if so. If the buttons work but the car will not start, the problem is the chip or the car, not the battery, and that is a job for an auto locksmith or the dealer.
When is a new case enough?
When the electronics work and only the shell, buttons or blade are damaged. A locksmith moves the circuit board and the chip from the old case into a new one, and cuts the new blade to match the old one. Nothing needs programming if the original board and chip are reused.
Buy a shell from the locksmith or ask them to check one you have bought. Cheap shells online vary in fit and in the quality of the blade, and a blade that will not cut cleanly is wasted money.
What does a replacement car key fob cost?
A new key, cut and programmed, costs about £100 to £282. WhoCanFixMyCar's 2026 booking data gives an average of £281.78, and StageMyCar, a trade blog, puts locksmith prices at £100 to £250 against £150 to £500 or more at a dealer. Programming on its own averaged £250.33 on WhoCanFixMyCar in 2026.
A keyless smart key is at the top of the range or above it, and a plain transponder key with no remote is at the bottom. Ask for the price split into the key, cutting and programming, and whether VAT is included.
Should you buy a fob online and have it programmed?
Sometimes, but ask a locksmith before you order. Many locksmiths will programme a key you supply, but some will not, because a cheap blank can fail to accept programming and the customer then blames the person who tried. Others charge the same either way.
Check that the fob is for your exact make, model, year and market, that the frequency matches, and that it can be programmed to the car at all. Some cars only accept keys through the maker's systems; since 1 April 2026 the UK SERMI scheme has opened that route to approved independent operators for some brands, as Motor Trader reported.
Common questions
Why does my car start but the fob buttons do not work?
Usually a flat fob battery. The immobiliser chip often works without the battery, so the car starts while the remote functions stop. Try a fresh battery of the type the handbook names.
Can a broken car key fob be repaired?
Often. A cracked case or worn buttons can be fixed by moving the electronics into a new shell. A board damaged by water or a fall usually means a new key.
Do I need to go to a dealer for a new fob?
Not for many cars. An auto locksmith can supply and programme most fobs. Some newer models and brands only accept keys through the maker's systems, so ask the locksmith with your make, model and year.
Does changing the battery wipe the fob?
For most cars, no. Some need the remote re-syncing after a battery change, and the handbook says if so. If it still will not work, ask an auto locksmith to test it.