Home › Services › Car Immobiliser Worthing
Car Immobiliser Worthing With Lost Keys Deleted and the Immobiliser Reset
Your car immobiliser decides which keys can start the engine. When a key is lost or stolen, it is deleted from the car and the immobiliser reset, so only the keys you hold will start it. Worthing Auto Locksmith does it at the car, with no tow.
Car Immobilisers in Worthing
A car immobiliser is the electronic lock on the engine. Each time you start the car, it asks the chip in the key for a code, and it only lets the engine run if the code is one it has stored. Every new car sold in the UK since 1998 has one, and many older cars do too.
Key Deletion and Immobiliser Reset, Explained
The immobiliser keeps a list of the keys it trusts. Key deletion takes a lost or stolen key off that list. An immobiliser reset clears the list and programs back only the keys you still hold. Both are done through the diagnostic port at the car.
Factory and Aftermarket Immobilisers
Almost every car has a factory immobiliser built into its electronics, and that is what this page covers. Some owners add an aftermarket immobiliser or tracker for extra security or for their insurer. Whether one suits your car is confirmed on the call.
Why a Lost or Stolen Key Should Be Deleted
A lost key still works. Whoever finds it can open the car and, on most cars, start it. Changing nothing is the biggest risk after a key goes missing.
If the Keys Were Stolen
Report it to the police and note the crime reference, then have the stolen key removed the same day. If you have no key left at all, a new one is made first, which is lost car keys.
After Buying a Used Car
A used car often comes with one key, and nobody knows where the others went. Deleting the unknown keys and adding a spare car key leaves you in control of every key that can start it.
After a Relay Theft Attempt
If someone has tried to steal a keyless car, a check of the stored keys shows whether an extra key was added. Any key you do not hold is removed.
How Key Deletion Works at Your Car
The whole job happens through the diagnostic port, with nothing taken apart on most cars.
The Stored Keys Are Read
The immobiliser is read and the number of keys it trusts is shown. This alone tells you whether a key you do not hold is still registered.
The Missing Keys Are Removed
The list is cleared and the keys you still hold are programmed back, which uses the same routine as car key programming.
Remotes Are Paired Again
The remote buttons are paired to the car again, so a lost remote can no longer unlock the doors.
Everything Is Tested
Each remaining key is tested on the doors, boot and engine before you pay.
How Many Keys Your Car Knows
Most cars store a fixed number of key slots. A quick read of the immobiliser shows how many are in use, which is the simplest security check there is.
| What the car shows | What it means | What to do |
|---|---|---|
| The same number of keys you hold | No unknown key is registered | Nothing, unless a key is lost later |
| More keys than you hold | A key you do not have can still start the car | Delete the missing keys |
| Fewer keys than you hold | One of your keys is not registered | Program it back to the car |
| No free slots left | The car cannot take another key | Delete an old key first, then add the new one |
Where the Immobiliser Sits in Different Cars
The immobiliser is not always a separate box, which is why the method changes from car to car.
Built Into the Engine ECU
On many cars the immobiliser lives inside the engine computer. Keys are added or deleted through the diagnostic port.
A Separate Module
Older BMWs and some other makes keep it in its own module, which is read before keys are changed.
Part of the Keyless System
On keyless cars the body control module and the keyless system both hold key data, and both are updated.
Vans
Vans use the same systems as cars, and keys for the Transit, Sprinter and Vivaro are covered under van key replacement.
Immobiliser Fault Symptoms and What They Mean
Not every car that will not start has an immobiliser fault. These are the signs that point to one, and what usually causes each.
| What the car does | What it usually means | What to check or fix |
|---|---|---|
| The engine cranks but will not start | The immobiliser is not accepting the key | Check the key chip, then the reader |
| The key or car symbol light stays on | The car cannot see a valid key | A diagnostic check of the key and immobiliser |
| The security light keeps flashing | The immobiliser is armed and refusing the key | Key chip test, then the antenna ring |
| The car starts some days and not others | A weak chip or a failing antenna ring | Test both before replacing anything |
| The remote works but the engine will not run | The remote is fine, the chip is not | Transponder key programming |
What Causes Immobiliser Faults
Six causes account for most immobiliser faults, from the cheapest to fix to the most expensive.
- A flat or damaged key battery, which stops a keyless car seeing the key.
- A worn or damaged chip in the key.
- A faulty antenna ring, the reader around the ignition.
- An ECU fault or corrupted data.
- A body control module fault.
- Water or corrosion in the key or the wiring.
A Worn Ignition Is Sometimes the Real Fault
If the key will not turn at all, the problem is mechanical, not electronic, and needs an ignition barrel repair rather than immobiliser work.
A Locked Steering Wheel on Some Cars
On many Mercedes and some other cars, the electronic steering lock is part of the immobiliser system. A fault there is steering lock replacement.
Immobiliser Repair Cost in the UK
The cost depends on which part has failed, which is why diagnosis comes first. These are typical UK figures.
| Repair | Typical price |
|---|---|
| Key fob battery | £2 to £5 |
| New key chip, programmed | £80 to £250 |
| Antenna ring | £50 to £150 |
| ECU repair by a specialist | £150 to £400 |
| Full ECU replacement at a dealer | £500 to £1,500 or more |
Deleting a lost key and resetting the immobiliser is usually far cheaper than any ECU work. The price for your car is agreed in writing on the call.
How an Immobiliser Fault Is Diagnosed
Guessing costs money, so the fault is found before any part is changed. The same five checks are made every time.
- A full system scan for stored fault codes.
- A key chip signal test, to see if the key is being read.
- An ECU communication check.
- A security code check, to see if the stored data is intact.
- Live data watched while the key is presented.
Start With the Cheapest Fix
If the key battery is the problem, a new one fixes it for a few pounds. A remote that still fails after a new battery needs a remote car key repair.
Can You Reset a Car Immobiliser Yourself
Rarely. Disconnecting the battery does not reset an immobiliser, because the key list is kept in memory that survives it. A few older cars have a relearn routine in the handbook, but it only works with a key the car already trusts.
Trying random resets can lock the immobiliser for a set time or corrupt its data, which turns a cheap job into an expensive one. If the car will not start at night or at the roadside, the 24 hour emergency auto locksmith covers every hour.
Your Call to a Secure Car
Every immobiliser job follows the same four steps.
Tell Us What Happened
Lost key, stolen key or a car that will not start, with the registration.
Price Agreed in Writing
The job is confirmed and the price agreed before a van leaves.
Ownership Checked at the Car
The V5C and photo ID are checked before the immobiliser is touched.
Keys Deleted or Fault Fixed
Missing keys removed or the fault repaired, and every key tested.
Areas We Cover for Car Immobiliser Worthing
Immobiliser work is done at the car across 15 towns and districts in BN11 to BN17, BN43, BN44, BN5 and RH20. Arrival times are listed under areas we cover, and the full key service is explained under car key replacement.
Car Immobiliser Questions Answered
The questions asked most about immobilisers, from deleting a lost key to warning lights and resets.
How much does an immobiliser repair cost?
It depends on the fault. A new key chip typically costs £80 to £250, an antenna ring at £50 to £150 and a specialist ECU repair at £150 to £400.
Why is my immobiliser light flashing and the car will not start?
The car is not recognising the key. The chip may be damaged, the key battery flat or the reader around the ignition faulty. A diagnostic check finds which.
How many keys does my car have programmed?
The car can tell you. A diagnostic check shows how many keys are stored, which is worth knowing after buying a used car.
Should I delete my old keys after my car keys were stolen?
Yes, the same day. Report the theft to the police, then have the stolen key removed from the car so it can no longer start it.
My key got wet and now the car will not start. What should I do?
Dry it and try the spare first. Water can damage the chip or the circuit. Often the electronics survive and only need a key fob repair, which costs far less than a new key.
Can a lost car key be deleted from the car?
Yes, on most cars. The lost key is removed from the immobiliser memory, so it no longer starts the engine even if someone finds it.
Does disconnecting the battery reset the immobiliser?
No. The key data is stored in memory that survives a battery disconnect. A reset needs diagnostic equipment.
Do all cars have an immobiliser?
All new cars sold in the UK since 1998. Many cars from the mid 1990s have one too.
Can you fit an aftermarket immobiliser?
Ask on the call. Whether an extra immobiliser suits your car and your insurer is confirmed before anything is booked.
Will my remaining keys still work after a reset?
Yes. The keys you still hold are programmed back to the car and tested before the van leaves.
Is immobiliser work done at the car in Worthing?
Yes. Key deletion and immobiliser resets are done at the car across Worthing and West Sussex, with no tow to a garage.
Lost a Key? Have It Deleted From Your Car
Give the registration and say which keys you still hold. The job is confirmed and the price agreed in writing before a van leaves.