Using Hand Held Tester (HHT)
WARNING: This page is about a different car, the 2002 Mercedes-Benz G500. However, it is still accessible from the selected car via links, so may be relevant.
Turn ignition off. Connect HHT to 38-pin diagnostic connector located in right rear of engine compartment. Turn ignition on. Follow manufacturer's instructions for reading fault codes. If no fault codes are present, but vehicle is experiencing a problem, go to TROUBLE SHOOTING - NO CODES (ENGINE 113 - G500) article.