See Figures 1 and 2
If your car is equipped with SRS, observe the following rules when performing electrical diagnosis:
If you are not absolutely sure of the identity of a component, leave it alone.
Know where a wire goes before applying voltage or checking resistance.
Turn the ignition to
and disconnect the negative battery cable before disconnecting any wiring or electrical connectors inside the car.
Be sure that the integrity of the SRS wiring is not disturbed during the installation of accessories such as CB radios, phones, audio equipment, etc.
If the steering wheel must be removed, the bag assembly must first be removed and disconnected from the center of the wheel. Put the unit to the side and DO NOT attempt to check resistance at the inflator.
On 780 series, ALWAYS disconnect the 4-pin yellow connector at the lower part of the steering column near the center console. The front seat belts are also part of the SRS system. If any diagnostics must be done to the seat belt system, disconnect the seat belt tensioners (grey connectors under the driver's seat) before doing any work.
On the 760 series, ALWAYS disconnect the 4-pin yellow connector (shown below) before doing ANY electrical diagnostic work.
Do not disconnect the main lead to the sensor box under the seat.
Volvo specifically recommends against anyone other than factory-trained personnel attempting repairs or diagnosis on the SRS system.
Fig. Fig. 1: Always unplug the yellow connector before performing any electrical diagnostic work-1988 760 with SRS shown
Fig. Fig. 2: Location of SRS connectors-1987 780 shown