The SRS (Supplemental Restraint System) is designed to restrain the
driver in the seat, while the SIPS (Side Impact Protection System) is
designed to cushion the driver from a side impact. Therefore, the SIPS
cannot be part of the SRS because it does not restrain the driver in
the seat. Even seat belts can be considered part of the SRS system,
though, so it does cover a broader range of devices than just the front
airbags.

However, to save on costs and space, for diagnostic purposes, the SRS
warning light on the dash represents all airbags in the car, even the
SIPS ones. So if your SRS light is on, it is entirely likely that it is
indicating a problem with the SIPS airbag.

One last item though...have your mechanic check all of the wiring in
the car having to do with the airbags and that light. On my 1998 V70XC
the light came on about eight months ago, and my mechanic and I went
through a complicated cycle of replacing all of the mechanical parts of
the airbags, eventually replaceing each individual airbag, and finally
I took it to another mechanic who diagnosed it as a faulty wiring
harness...who would have thought? So I spent upwards of $3,000 for a
simple repair that should have only cost $750. Oh well.

Good luck!