Crash Control Module: Description and Operation

Location:

NOTE: Do not open crash shut-off relay


Purpose
The purpose of the crash shut-off relay is to disconnect the power supply from the generator/battery (c. 30) in the event of an accident and thereby prevent a fire resulting from a short circuit. It serves as a type of battery isolation switch.

Function
In the event of an accident the crash shut-off relay is actuated by the airbag triggering unit when the airbag is actuated. This destroys one of two fuses iii the crash shut-off relay thereby interrupting the connection between the generator and battery. This circuit is also interrupted when the ignition is switched OFF or the vehicle shut off.

In normal operation the crash shut-off relay is actuated via the ignition lock (c. 15) ignition ON and connected ground (c. 31). This actuation connects the generator with the battery. If a malfunction occurs in the leads from C. 15 or C. 31 (e.g. discontinuity), the battery is not charged when the engine is running. The final result is complete failure of the vehicle electrical system due to the continuously decreasing electrical system voltage resulting from the battery not being charged.


NOTE: A defect in the crash shut-off relay and therefore an interruption in the battery charging operation is not indicated to the driver by the charge indicator lamp.