A ECU (Engine Control Unit) is an electronic control system that manages and regulates the engine performance and efficiency via a series of actuators and sensors.

The ECU processes real time data taken from sensors such as air intake, exhaust gas, throttle position and crankshaft position, compares it to a ‘map’ or ‘lookup table’ and then adjusts components accordingly via actuators. Adjustments include changes to the engines timing, fuel/air mix and idle speed.

Some Engine Control Units also handle additional elements such as cruise control, anti-theft and anti-skid.

ECU’s are located within the dashboard or engine bay. It is often possible to ‘read’ or interrogate your cars ECU using a laptop computer with relevant software and cable or a dedicated reader via a connection port which is usually located in the dashboard. This method is used by mechanics for diagnosis of engine 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. Bad data from failed or degraded sensors are also common cause of ECU related faults.