The Sagem AC4 airbag system, designed and manufactured by Sagem, fitted to all Freelanders. Airbag ECUs are often referred to as DCUs (Diagnostic Control Units) because of the fact that they do very extensive diagnostic tests themselves. This means that no dynamic information is made available, neither are there any outputs which can be driven. It does however have an extensive fault memory function which can be read and cleared. A vast array of settings are also available diagnostically together with the vehicle's VIN number.