Chassis Electrical

SUPPLEMENTAL RESTRAINT SYSTEM (AIR BAG)

General Information

Fig. 1: SRS system component location-Legacy

Some late model Subaru vehicles are equipped with an air bag system, to supplement the safety belts. When an impact at the front of the vehicle is greater than a set level in the air bag sensor, the sensor senses it and generates an electrical pulse to inflate the bag in the air bag module, preventing the drivers body from contacting the steering wheel.

The SRS air bag consists of an control unit, left and right front sensors, 2 safety sensors built into the control unit and an air bag module containing an air bag and inflator. The left and right front sensors and the 2 safety sensors are connected in parallel respectively, and the front sensors and safety sensors are connected in series, so the air bag will inflate if at least 1 front sensor and 1 safety sensor sense an impact at the same time.

The components of the SRS system are not owner serviceable and no attempts should be made to repair the system, however, when working on any of the electrical systems inside of the vehicle, the air bag system must be disarmed. This can be accomplished by following the disarming procedure given in this section.

All SRS electrical wiring harnesses and connections are covered with yellow outer insulation.

SYSTEM OPERATION
See Figures 2, 3 and 4

Fig. 2: SRS sensor flow chart

Fig. 3: SRS wiring diagram

Fig. 4: SRS wiring locations

The SRS is designed to deploy the air bag when the safing sensor and any of the 4 sensors (front crash zone sensor, center crash zone sensor, left crash zone sensor or tunnel sensor) simultaneously make contact, with the ignition switch in the ON position. Air bag deployment will occur in a frontal or near frontal impact of moderate to severe force.

The diagnostic unit monitors the SRS system and stores data, should any faults be detected in the system. When the engine is started or the ignition switch is in the ON or START position, the SRS warning light should illuminate for approximately 7 seconds and then turn OFF. This indicates that the system is operational.

Fig. 5: SRS components-SVX

Air Bag Module

The air bag module, located in the center of the steering wheel, contains a folded air bag and an inflator unit.

Spiral Cable

The spiral cable, located in the steering column, ensures an uninterrupted electrical circuit to the air bag module, while allowing rotation of the steering wheel. This cable is sometimes referred to as a clockspring.

Warning Lamp

The warning lamp, located in the instrument panel, indicates operational status of the SRS.

SRS Control Unit

The SRS control unit, monitors the SRS system and stores data, should any faults be detected in the system.

Air Bag Connector

The SRS system connectors use a double lock mechanism and a coupling error detection system. If the connector is not properly connected, the air bag warning light will illuminate on the instrument cluster.

The proper method for using these connectors is to press the release tab on the connector until the green lever pops up, this will unlock the connector. Then pull the connector apart while pushing the lever down. To reconnect the connectors, push the halves together until a click is heard then push the green lever down until another click is heard.

• Do not disassemble any air bag system components.
• Always carry an inflator module with the trim cover pointed away.
• Always place an inflator module on the workbench with the pad side facing upward, away from loose objects.
• After deployment, the air bag surface may contain sodium hydroxide dust. Always wear gloves and safety glasses when handling the assembly. Wash hands with mild soap and water afterwards.
• When servicing any SRS parts, discard the old bolts and replace with new ones.
• The SRS must be inspected 10 years after the vehicle's manufacture date shown on the certification label located on the left front door latch post.
• Always inspect the air bag sensors and steering wheel pad, when the vehicle has been involved in a collision (even in cases of minor collision) where the air bag did not deploy.
• Always use a fine needle test lead for testing, to prevent damaging the connector terminals.
• Never disconnect any electrical connection with the ignition switch ON unless instructed to do so in a test.
• Before disconnecting the negative battery cable, make a record of the contents memorized by each memory system like the clock, audio, etc., when service or repairs are completed make certain to reset these memory systems.
• Always wear a grounded wrist static strap when servicing any control module or component labeled with a Electrostatic Discharge (ESD) sensitive device symbol.
• Avoid touching module connector pins.
• Leave new components and modules in the shipping package until ready to install them.
• Always touch a vehicle ground after sliding across a vehicle seat or walking across vinyl or carpeted floors to avoid static charge damage.
• All sensors are specifically calibrated to a particular series.The sensors, mounting brackets and wiring harness must never be modified from original design.
• Never strike or jar a sensor, or deployment could happen.
• The inflator module must be deployed before it is scrapped.
• Any visible damage to sensors requires component replacement.
• Never bake dry paint on vehicle or subject the vehicle to temperatures exceeding 200°F (93°C), without disabling the air bag system and removing the inflator module, crash zone sensors, SRS diagnosis unit and the spiral cable.
• Do not interchange sensors between models or years.
• Do not install used air bag system parts from another vehicle.
• Never allow welding cables to lay on, near or across any vehicle electrical wiring.
• When ever any SRS parts are removed, always use new retaining bolts.
• Caution labels are important when servicing the air bag system in the field. If they are dirty or damaged, replace them with new ones.

Fig. 6: Air bag harness below steering column

Fig. 7: Disconnecting the air bag harness

Fig. 8: If disconnecting the harness from the control unit, construct a tab removal tool, and depress the tab until the green lever pops up

Be sure to properly disconnect and connect the air bag connector.

1. Turn the ignition switch to the OFF position.
2. Disconnect the negative battery cable.

3. Remove the lower lid from the steering column and disconnect the harness between the air bag module and spiral cable.

1. Reconnect the connector between the air bag module and spiral cable. Then install the lower steering column lid.
2. Reconnect the negative battery cable.
3. Turn the ignition switch to the ON position and observe the SRS warning light. The SRS warning light should illuminate for approximately 7 seconds, turn OFF and remain OFF for at least 45 seconds.
4. If the SRS warning light function as indicated in Step 3, the SRS system is functioning properly.

END OF SECTION