Transponder Replacement & ECU Resetting

Issues arising from lost transponder keys are far more complex than tradition issues associated with older vehicles.

Transponder keys and the ECU immobilizer system work hand in hand with one another as a high level anti-theft security measure found in many modern vehicles. They work together via signal based communication, where the transponder key and ECU must have matching signals for the vehicle’s engine to start.

What is a transponder key

Many car Manufacturers, post-1995, use transponder keys, which have an inbuilt chip that is used to communicate and deactivate the engine immobiliser. Transponder keys are essentially used as an extra anti-theft security measure for your vehicle.

Once the transponder key has been turned in the ignition, the ECU sends a low-level signal/code to the transponder circuit. The transponder circuit will then send a signal/code back, and if the code is incorrect, the car will not start. The code will often be incompatible as the wrong transponder key has been used. In newer cars, the transponder doesn’t even need to be put into the ignition, just inside the car for keyless starting and entry systems.

Transponder keys are far more reliable and secure than traditional automotive keys. Transponders can prevent hot wiring due to the fact that if the car does not detect the correct serial number on the key or does not receive the proper signal, then the vehicle will be immobilised.

Engine Control Unit (ECU)

The ECU is responsible for numerous vehicle functions, including the fuel supply, air management, fuel injection, ignition, and an engine immobiliser built within it as an anti-theft measure.Essentially the ECU is the brain/heart of any modern vehicle and if the ECU does not recognise the transponder key used within the ignition, the car engine will be immobilised and will not start.

Common Problems and Causes

Vehicle issues relating to the performance of a transponder key or the ECU immobiliser system are various as both do not function flawlessly. Both are essential for modern vehicles’ anti-theft measures yet are capable of malfunctioning, which can potentially leave you and your car stranded.

Key Symbol on Dashboard:

Most cars can detect and alert the driver of a malfunction with either the transponder key or the immobiliser control unit via a symbol on the dash.

Car not Starting:

This problem can be confused with engine issues. However, suppose the ignition is turned with the transponder key, yet there is no indication of the engine attempting to start. In that case, this may be a sign of a transponder key malfunction as the key may not be communicating correctly with the ECU.

Problems Locking and Unlocking Vehicle:

You may have a modern car where you use your remote transmitter to lock and unlock your vehicle. If your key malfunctions on an infrequent basis but then reverts to normal function, then it may be a sign of a faulty transponder key.


If you have lost, misplaced or had the keys to your vehicle stolen, our experienced team at Alchin Locksmiths can supply, cut and program new keys to your vehicle. We can also remove, reset and reinstall the ECU immobiliser system with our equipment on site, eliminating all existing keys from the immobiliser system, ensuring that the old keys cannot be used.

All this is done at your convenience at the vehicle location.


Let's Secure Your Vehicle

Our team at Alchin Locksmiths are equipped with the tools, parts and experience to replace your vehicle keys.  All it takes is a simple phone call and we will be on our way.


What should I do if I lose my car key?

You should first call us and make an immediate booking because we understand how frustrating and inconvenient losing your keys can be. Once a booking is made, our team will come straight to you wherever you may be.

How much does it cost for a replacement transponder key?

The price for a replacement transponder key will vary based on the complexity and specific type of issue at hand.

However, for specific pricing, give us a call, and we will offer an affordable replacement cost. Our prices are competitive and fair, especially compared to many car dealerships with a high chance they will charge a premium for a replacement key, in many instances,  the dealer employs us to perform the job for them.

Call Now 8283 3332