A <Model> central locking ECU (Electronic Control Unit) is a microcomputer or brain responsible for management and control of a car’s central locking and security system. All locking components including the lock mechanisms, lock barrels, lock levers, actuators, remote sensors and other lock controls are electrically connected to the ECU, allowing it to regulate and control the overall state of the system. The central locking ECU may also control electric window closure, vehicle immobiliser and alarm system.

A <Model> central locking ECU is located within the dashboard or engine bay. It is generally possible to ‘read’ or interrogate the central locking ECU using a laptop computer with relevant software and cable or a dedicated reader via a connection port usually located in the dashboard. This is the best method for diagnosis of central locking faults.
Like any electronic component an ECU can fail for a number of reasons including short circuits, dry solder joints, water damage or age. Diagnosis is generally much easier with the correct reader which can be used to obtain error codes from the ECU.