Mercedes-Benz S-Class Engine 256.9: How to Replace the Integrated Starter Alternator

The integrated starter alternator (ISG) on the Mercedes-Benz engine 256.9 is responsible for starting the engine and generating electricity to power the vehicle's electrical systems. It is a compact and efficient system that is integrated into the engine itself. To remove and install the ISG, the transmission and ISG control unit must first be removed, as well as the sensors of the intake and exhaust camshafts and the hose to the air filter. The ISG must be removed from under the vehicle and placed on a workbench for inspection. The ISG must be fixed to the engine and all screws, centering flange and seals must be replaced. It's important to refer to the WIS document for torque and rotation angle specification.