Head Airbags

Head Airbags

The SRS DCU registers a side impact via the side impact sensors, which are mounted at the base of the LH and RH B/C posts. The SRS DCU monitors the condition of the RH sensor (C0951) and the LH sensor (C0950) on YR and YG wires respectively. Both sensors are earthed on NB wires. When the SRS DCU registers a side impact above its threshold level, it will fire the relevant head airbag.

LH Front

The SRS DCU (C0256) provides a firing signal to the LH front head airbag (C1477) on a UY wire. An earth path is provided by the SRS DCU (C0256) on a Y wire.

RH Front

The SRS DCU (C0256) provides a firing signal to the RH front head airbag (C1478) on a W wire. An earth path is provided by the SRS DCU (C0256) on a UW wire.

LH Rear

The SRS DCU (C0256) provides a firing signal to the LH rear head airbag (C1474) on a B wire. An earth path is provided by the SRS DCU (C0256) on a Y wire.

RH Rear

The SRS DCU (C0256) provides a firing signal to the RH rear head airbag (C0948) on a UG then UR wire. An earth path is provided by the SRS DCU (C0256) on an R then G wire.

Occupancy Detector

The occupancy detector determines if there is a passenger occupying the front seat. If the front seat passenger is not detected, the front passenger airbag, and front passenger head airbag deployment is suspended in the event of an impact. All other SRS components will operate as normal.

The occupancy detector (C0962) is provided an auxiliary ignition feed from fuse 44 of the passenger compartment fuse box (C0586) on a PG wire, and is earthed on an NB wire. The occupancy detector (C0962) provides a pulsed voltage signal to the SRS DCU (C0256) on a WR wire. The signal consists of 7 bits. A signal of '0 00 00 01' informs the SRS DCU the front passenger seat is unoccupied. A signal of '0 11 11 01' informs the SRS DCU the front passenger seat is occupied.

Seat Belt Switches

The SRS DCU determines if the front seat belts are being used by monitoring the status of the seat belt switches. If the seat belt tongue is inserted into the buckle, the switch contacts close and battery voltage is supplied to the SRS DCU (C0256) on UW (LH) and UP (RH) wires. If the SRS DCU detects a seat belt is not being used, it will not fire the relevant seat belt pre-tensioner.