Air Bag Control Module: Description and Operation

A function of the DERM is to supply the deployment loop with a 36 volt loop reserve to ensure sufficient energy to deploy the air bag if the ignition feed to the arming sensor is lost during a frontal collision.
Another function of the DERM is electrical system diagnostics. The DERM can detect circuit and component malfunctions within the deployment loop. Voltage drops across components within the loop are measured during non-deployment conditions. If the monitored voltages fall outside of the expected limits, the DERM will indicate a malfunction through the storage of a diagnostic trouble code and the illumination of the air bag warning light.