Air Bag Supplemental Restraint System (SRS) Components

Air Bag and Safety Belt Pretensioner Supplemental Restraint System (SRS)
The air bag Supplemental Restraint System (SRS) is designed to provide increased collision protection for front seat occupants in addition to that provided by the three-point safety belt system. Safety belt use is necessary to obtain the best occupant protection and to receive the full advantages of the SRS.

The air bag Supplemental Restraint System (SRS) components are shown in the illustration.

Air Bag Supplemental Restraint System (SRS) Components:

Air Bag Supplemental Restraint System (SRS) Components

The Driver Air Bag Module:

Driver Air Bag Module:

Driver Air Bag Module

^ is replaced as an assembly.
^ is mounted in the center of the steering wheel.

Steering Wheel Trim Cover
The steering wheel trim cover:
^ encases the driver air bag module and horn switch.
^ has tear seams that separate to allow inflation of the air bag.
^ must not be repainted for any reason.
^ is a component of the driver air bag module and is not repaired separately.

Air Bag
The air bag:
^ is constructed of nylon.
^ is a component of the driver air bag module and is not replaced separately.

Inflator
The inflator:
^ receives electrical energy when the air bag sensors close.
^ contains an igniter that converts the electrical signal to thermal energy (heat), causing the ignition of the inflator gas generant.
^ inflates the air bag with nitrogen gas after the chemical reaction takes place.
^ is a component of the driver air bag module and is not replaced separately.

Mounting Plate and Retainer Ring
The mounting plate and retainer ring:
^ attach and seal the air bag to the inflator.
^ attach the trim cover.
^ mount the entire driver air bag module to the steering wheel.
^ are components of the driver air bag module and are not replaced separately.

The Passenger Air Bag Module:

Passenger Air Bag Module:

Passenger Air Bag Module

^ is replaced as an assembly.
^ is mounted in the RH side of the instrument panel.

Deployment Door
The deployment door.
^ is textured and painted to match the surface of the instrument panel.
^ is attached to the reaction housing with two nylon web straps and to the instrument panel with spring clips.
^ disengages from the instrument panel when the air bag inflates and moves out of the way during deployment.
^ is a component of the passenger air bag module and is not replaced separately.

Air Bag
The air bag:
^ is constructed of nylon.
^ is a component of the passenger air bag module and is not replaced separately.

Inflator
The inflator:
^ receives electrical energy when the air bag sensors close.
^ contains an igniter that converts the electrical signal to thermal energy (heat), causing the ignition of the inflator gas generant.
^ inflates the air bag with nitrogen after the chemical reaction takes place.
^ is a component of the passenger air bag module and is not replaced separately.

Reaction Housing
The reaction housing:
^ provides support for the inflator.
^ provides a reaction surface for the passenger air bag module.
^ is used to attach the deployment door with tethers.
^ contains mounting brackets that attach the passenger air bag module to the instrument panel.
^ is a component of the passenger air bag module and is not replaced separately.

The air bag Electronic Crash Sensor (ECS)
The air bag Electronic Crash Sensor (ECS) module performs the following functions:
^ deploys the air bags and seat belt pretensioners in the event of a deployable crash.
^ monitors the air bag Supplemental Restraint System (SRS) for faults.
^ illuminates the air bag indicator if a fault is detected.
^ flashes the air bag indicator to indicate the Lamp Fault Code (LFC) detected.
^ communicates through the Data Link Connector (DLC) the current and historical Diagnostic Trouble Codes (DTCs).
^ activates a chime or buzzer if the air bag indicator is not available.

The ECS, together with the primary crash sensor, determines when to deploy the air bags and belt and buckle assembly pretensioners.

The ECS monitors the SRS for possible faults. If a fault is detected while the ignition switch is in the RUN position, the ECS will illuminate the air bag indicator located in the instrument cluster. When the ignition is cycled (turned off then turned on), the air bag indicator will flash the two-digit Lamp Fault Code (LFC). The air bag indicator will flash the LFC twice, then it will remain illuminated for the rest of the key cycle. The ECS will also communicate the current and historical DTCs through the Data Link Connector (DLC), using the scan tool. If the air bag indicator does not function, and the system detects a fault condition, the ECS will activate an audible chime or buzzer. The chime is a series of five sets of five tone bursts. The buzzer is a five-seconds-on, five-seconds-off buzzing noise. If the chime or buzzer is heard, the SRS or the air bag indicator requires service.

Lamp fault codes are prioritized. If two or more faults occur at the same time, the fault having the highest priority will be displayed first. After that fault has been corrected, the next highest priority fault will be displayed.

The ECS includes an internal backup power supply. This feature provides sufficient backup power to deploy the air bag in the event the battery or battery cables are damaged in a collision before the safing and primary crash sensors close. The backup power supply will deplete its stored energy approximately 1 minute after the battery ground cable is disconnected.

There are three types of E-Series ECS modules: a two-ignitor system for a school bus, a three-ignitor system for a cargo van and a four-ignitor system for a passenger van. These ECS modules have unique part numbers and are not interchangeable.

Electrical System
The electrical system that supports the air bag Supplemental Restraint System (SRS):
^ is powered from the battery and the ignition.
^ provides the electrical path from the primary crash sensor to the air bag Electronic Crash Sensor (ECS) module.
^ provides the electrical path from the ECS to the air bag modules and belt and buckle assembly pretensioners.
^ provides the electrical path from the ECS to the air bag indicator and Data Link Connector (DLC).

Sensors

WARNING: THE ECS AND PRIMARY CRASH SENSOR ORIENTATION IS CRITICAL FOR PROPER SYSTEM OPERATION. IF A VEHICLE EQUIPPED WITH AN SRS SYSTEM HAS BEEN INVOLVED IN A COLLISION WHERE THE RADIATOR GRILLE, FRAME RAILS OR RIGHT COWL PANEL HAS BEEN DAMAGED, INSPECT THE MOUNTINGS AND BRACKETS FOR DEFORMATION. IF DAMAGED, THE PRIMARY CRASH SENSOR OR ECS MUST BE REPLACED WHETHER OR NOT THE AIR BAG MODULES HAVE DEPLOYED. IN ADDITION, MAKE SURE THE AREA OF THE PRIMARY CRASH SENSOR MOUNTING IS RESTORED TO ITS ORIGINAL CONDITION.

NOTE:
^ The safing sensor is internal to the ECS and is not serviced separately.
^ If the primary crash sensor is undamaged after a collision, it will automatically reset and can be reused.

The SRS contains three sensors located in the following spots:
^ the ECS, mounted behind the RH cowl side trim panel.
^ the primary crash sensor mounted on the center radiator support.
^ the safing sensor, which is internal to the ECS.