ETR and airbag control unit - task - GF91.60-P-4006-02PP

The restraint systems control unit (N2/7) has the following tasks:

• Self test with "circuit 15R ON" and constant system monitoring while driving
• Storage of up to ten recognized faults in the diagnostic fault memory.
• Detection of front passenger seat occupancy and child seat recognition system (B48)
• Recording of status of driver seat belt buckle restraint systems switch (S68/3) and front passenger seat belt buckle restraint systems switch (S68/4)
• Actuation of airbag indicator and warning lamp (A1e15)
• Actuation of Airbag Off automatic child seat recognition indicator lamp (N72/1e1)
• Prevention of false deployments in normal vehicle operation through additional safety sensor
• Detection and evaluation of the collision according to type and severity via integrated sensors and via the separate sensors for the left sidebag and windowbag (A53/1) and right sidebag and windowbag (A54/1)
• Output of the trigger pulses to the corresponding airbag and belt tensioning units taking the corresponding parameters into account
• Engine switch-off if the airbag is deployed via the ME-SFI ([ME] control unit (N3/10) or CDI control unit (N3/9)
• Initiation of an emergency call via the telephone and TELE AID transmitter and receiver unit, D2B (A35/17) in the event of an airbag deployment and severe rear-impact collision
• Ensuring the energy reserve in the event of an interruption to the voltage supply for 150 ms (To protect the occupants and the rescue personnel, deployment is no longer possible at the latest one second after the battery has been disconnected.)
• Records up to 5 crash logs

To safeguard against faulty triggering under normal driving conditions, e.g. by electromagnetic pollution, the restraint systems control unit (N2/7) is equipped with an additional safety sensor. This sensor, which also has the function of a switch, only responds in the event of a deceleration which has been caused by a head-on collision. It is looped into the triggering circuits for driver's and front passenger airbag and conducts the entire triggering current if the latter are deployed. The safety sensor is not looped into the triggering circuits for the driver and front passenger emergency tensioning retractor, however its switching state is queried by the restraint systems control unit (N2/7) before deploying the emergency tensioning retractors. The emergency tensioning retractors are triggered only if it responds to the deceleration as it occurs.

In the event of accidents with side impacts, the safety sensor remains without function. Here, an additional safeguard against false deployments is provided by a plausibility check performed in the control unit. Here the signals received by the left sidebag and windowbag sensor (A53/1) and right sidebag and windowbag sensor (A54/1) are compared with the internally measured acceleration values.