Description & Operation

WARNING: This page is about a different car, the 1997 Mercedes-Benz E420, 1997 Mercedes-Benz E320, and 1997 Mercedes-Benz E300. However, it is still accessible from the selected car via links, so may be relevant.

WARNING: To avoid injury from accidental air bag deployment, read and carefully follow all WARNINGS and SERVICE PRECAUTIONS .

All models are equipped with Supplemental Restraint System (SRS). The main components of SRS are a driver air bag module, passenger air bag module, control unit, SRS warning light, driver knee bolster, passenger knee bolster, and Emergency Tensioning Retractor (ETR) seat belt assembly. Additionally, E Class vehicles provide driver-side and passenger-side impact protection by side air bags which are mounted in the driver-side and passenger-side doors.Each of the door mounted side air bags utilize sensors which recognize lateral acceleration during side impact and signal this to the control module. See Fig 1.

Fig 1: SRS Component Locations

Courtesy of MERCEDES-BENZ OF NORTH AMERICA

Both SRS and ETR are electronically activated by a single control unit if a moderately severe to severe frontal collision occurs. There are 2 thresholds which must be exceeded to trigger an ETR action, air bag deployment, or both. If a moderately severe frontal collision occurs exceeding 1st triggering threshold where protection from safety belt is sufficient, only Emergency Tensioning Retractor (ETR) is activated if safety belt is buckled. If a moderately severe frontal collision occurs exceeding 1st triggering threshold where protection from safety belt is sufficient, but safety belt is not buckled, air bag is deployed and ETR is not activated.

If a severe frontal collision occurs exceeding 2nd triggering threshold where protection from safety belt is insufficient, air bag is deployed. ETR is activated if safety belt is buckled. If safety belt is not buckled, ETR is not activated when 2nd triggering threshold is reached. Passenger air bag will deploy even if passenger seat is not occupied when a triggering threshold is exceeded. If during a severe frontal collision the power supply is interrupted, the driver and passenger air bag can still be deployed, but ETR cannot be activated.

The side air bag on the driver-side deploys whenever the driver-side air bag module is deployed and when there is a substantial side impact crash. The air bag on the passenger-side will activate only when a sensor (Occupied Seat Recognition Sensor) in the passenger seat sends a signal to the control module that the passenger-side seat is occupied. During a collision, the side air bag will then deploy.