An immobiliser is an electronic security system that prevents the engine from starting unless the vehicle recognises an authorised key or security credential.

Possible signs include a key-not-recognised message, a flashing security light, intermittent starting, an engine that cranks but does not start or an engine that starts and immediately stops. These symptoms can also have other causes, so diagnosis is required.

Possible causes include a damaged key transponder, low vehicle voltage, signal interference, a faulty reader coil, damaged wiring, programming loss or a communication problem between control modules.

The immobiliser may be preventing continued engine operation because it cannot authenticate the key. Fuel, ignition, sensor and engine-management faults can produce similar symptoms, so the vehicle should be tested.

Low or unstable voltage can cause warning messages, communication faults or loss of certain stored settings on some vehicles. If the problem began after a flat battery or battery replacement, mention this when booking.

Yes. If the vehicle starts with the spare key, the original key may be damaged or no longer recognised. Bring all available keys when attending the workshop.

A1 Diagnostics can provide key-coding and programming services for many vehicles. Capability depends on the manufacturer, model, security system and availability of the required authorised access.

This may be possible on supported vehicles by updating the list of authorised keys. Customers will need to provide proof of identity and ownership before security-related work is undertaken.

Some faults can be repaired, while others require module replacement, programming or synchronisation. Diagnosis is needed before the correct option can be recommended.

A replacement ECU frequently requires vehicle-specific programming, configuration or immobiliser synchronisation before the engine will start. The exact procedure depends on the vehicle.

The outcome depends on the vehicle, warning displayed and applicable MOT inspection requirements. A warning light should be diagnosed even where it does not directly result in an MOT failure.

An intermittent immobiliser fault could leave the vehicle unable to restart. If the engine cuts out, will not start reliably or the vehicle cannot be driven safely, arrange appropriate recovery rather than continuing the journey.

The cost depends on the vehicle and whether the fault involves diagnosis, wiring repair, key programming, a reader component or a control module. Provide the vehicle registration and fault details so A1 Diagnostics can assess the enquiry.

Diagnostic time varies according to the vehicle, symptoms and complexity of the fault. Intermittent problems or communication faults may require more testing than a straightforward key-programming procedure.

Bring all available keys, proof of identity and proof that you own or are authorised to manage the vehicle. Details of recent battery, ECU, body control module or electrical work can also help the diagnostic process.