SYSTEM OPERATION AND COMPONENTS
The Supplemental Restraint System (SRS) is designed to supplement the front seat belts to help reduce the risk or severity of injury to the driver by activating and deploying a driver's-side air bag in certain frontal collisions.
The SRS consists of: left front and right front impact sensors (located on the right and left radiator support panels); air bag module (located in the center of the steering wheel). The air bag module contains a folded air bag and an inflator unit. The SRS also contains: a SRS diagnosis unit with a safing impact sensor (located in front of the shift lever); a SRS warning light to indicate operational status of the SRS (located on the instrument panel); a clock spring (mounted behind the steering wheel); and wiring.
The SRS is designed so that the air bags will deploy (inflate) when the safing sensor, plus either or both of the left front and right front impact sensors simultaneously activate while the ignition switch is in the ON position. These sensors are designed to be activated in frontal or near-frontal impacts of moderate to severe force.
The diagnosis unit monitors the SRS system and stores data concerning any detected faults in the system. When the ignition key is in the ON or the START position, the SRS warning light should illuminate for about 7 seconds and then turn off. That indicates that the SRS system is in operational order. If the SRS warning light does any of the following, immediate inspection by an authorized dealer is needed:
If a vehicle's SRS warning light is in any of these three conditions when brought in for inspection, the SRS system must be inspected, diagnosed and serviced by a qualified automotive mechanic.
- In order to avoid injury to yourself or others from accidental deployment of the air bag during servicing, have a qualified automotive mechanic work on the system.
Do not use any electrical test equipment on or near SRS components, except for the following:
MB991502 Scan tool (MUT-II)
Never attempt to repair the following components:
Front impact sensors
If any of these components are thought to be faulty, take the vehicle to a qualified mechanic in order to have them replaced.
- Do not attempt to repair the wiring harness connectors of the SRS. If any of the connectors are found to be faulty, replace the wiring harness.
- After disconnecting the battery cable, wait 60 seconds or more before proceeding with any work on the SRS system. The system is designed to retain enough voltage to deploy the air bag for a short time even after the battery has been disconnected, so serious injury may result from unintended air bag deployment if work is done on the SRS system immediately after the battery cables are disconnected.
- SRS components should not be subjected to heat over 200°F (93°C), so remove the front impact sensors, SRS diagnosis unit, air bag module and clock spring before drying or baking the vehicle after painting.
- Whenever you finish servicing the SRS, check the SRS warning light operation to make sure that the system functions properly.
- Make certain that the ignition switch is OFF when any scan tool is connected or disconnected.
- If the SRS components are removed for the purpose of inspection, sheet metal repair, painting or other work, they should be stored in a clean, dry place until they are reinstalled.
Serious injury can result from unintentional air bag deployment, so it is best to have the SRS components and system worked on by a qualified mechanic.
DISARMING AND ENABLING THE SYSTEM
To disarm the SRS system, disconnect the negative battery from the battery and wait at least 60 seconds. Waiting for 60 seconds after disconnecting the cable is imperative because the SRS control module holds voltage. The module is designed to hold voltage, so that if, during a frontal collision, one or more of the battery cables is severed, the module will still have the voltage needed to deploy the air bag.
To arm the SRS system, reconnect the negative battery cable to the battery. Turn the ignition key ON . Make sure the SRS warning light illuminates for about 7 seconds, turns off and then remains off for at least 45 seconds. If the warning light does anything other than this, the SRS system is not functioning correctly and should immediately be taken to a qualified automotive mechanic.