Air Bag Systems: Description and Operation
Airbag Control Module
The Airbag Control Module (ACM) contains the safing sensor and energy reserve capacitor. The safing sensor is located inside the ACM. The module is mounted on the tunnel/floor pan in front of the gear shift lever and below the center of the instrument panel. The safing sensor protects against accidental airbag deployment. The ACM monitors the system to determine the system readiness. The ACM will store sufficient energy to deploy the airbags for up to one second after the battery is disconnected. The ACM contains on-board diagnostics, and will illuminate the AIRBAG warning lamp in the cluster when a fault is detected. The warning equipment is tested for six to eight seconds every time the vehicle is started.
Clockspring
The clockspring is mounted to the steering column behind the steering wheel. The clockspring is used to maintain a continuous electrical circuit between the wiring harness and the:
- Driver's airbag module
- Speed control switches
- Horn switch
The clockspring consists of a flat, ribbon like, electrically conductive tape which winds and unwinds with the steering wheel rotation.
Driver And Passenger Airbag Module
WARNING: Never disassemble the driver or passenger airbag module, there are no serviceable parts with in the modules.
The Driver Airbag Module located on the steering wheel is the most visible part of the system. The airbag module contains a housing to which the cushion, inflator and cover are attached to.
The driver side inflator assembly is mounted from the back of the module housing. When supplied with the proper electrical signal the inflator assembly will produce a gas and discharge it directly into the cushion. A protective cover is fitted to the front of the Driver Airbag Module and forms a decorative cover in the center of the steering wheel. The Driver Airbag Module is mounted directly to the steering wheel.
The Passenger Airbag Module is located beneath the decorative cover of the instrument panel, facing the passenger seat.
The passenger inflator assembly is within the module housing. The module is mounted to the instrument panel retainer and support structure. When supplied with the proper electrical signal the inflator will produce a gas and discharge it directly into the cushion. A protective cover is fitted into the instrument panel over the airbag module and forms a decorative cover.
Vacuum Heater And A/C Outlets:
Front Impact Sensors
The Driver/Passenger Airbag System is a supplemental safety device designed to help protect the driver/passenger from serious injury, caused by a frontal impact of the vehicle.
The two front impact sensors provide verification of the direction and severity of the impact. The sensors are mounted to brackets on the left and right side of the frame tips near the battery.
The impact sensors are threshold sensitive switches that complete an electrical circuit when an impact provides a sufficient acceleration to close the switch. The sensors are CALIBRATED FOR THE SPECIFIC VEHICLE and react to the severity and direction of the impact.
Passenger Airbag On/Off Switch
A Passenger Airbag ON/OFF Switch located in the right instrument panel endcap, allows the passenger side airbag module to be disabled when certain child restraint devices are being used in the right seating position. The passenger airbag ON/OFF switch is equipped with a key cylinder so that the switch position can only be changed using an ignition key. When the ignition switch is in the ON position and the passenger side airbag is disabled, a Light-Emitting Diode (LED) illuminates a "PASS AIRBAG OFF" indicator lamp in the instrument cluster.
To actuate the passenger airbag ON/OFF switch, open the passenger door, insert the ignition key in the switch key cylinder. The switch key cylinder is then rotated with the ignition key to its clockwise stop (the key cylinder slot will be aligned with the OFF label on the instrument panel endcap) to disable the passenger side airbag. When the passenger air- bag ON/OFF switch key cylinder is rotated with the ignition key to its counterclockwise stop (the key cylinder slot will be in a vertical position), the instrument cluster indicator lamp will be extinguished and the passenger side airbag module will once again be enabled.
WARNING: The key must always be removed from the passenger airbag on/off switch key cylinder after the switch has been used. Never leave a key in the passenger airbag on/off switch key cylinder.
The passenger airbag ON/OFF switch cannot be adjusted or repaired and, if faulty or damaged, the switch assembly MUST be replaced.
WARNING: In the event of an airbag deployment, the passenger airbag on/off switch "MUST" be replaced.
AIRBAG SYSTEM
Functional Operation
The airbag system was designed to provide increased driver and passenger protection if the vehicle is involved in a front-end collision. The system was designed to be, and is most effective when used in conjunction with the seat belt system. The passenger side airbag assembly utilizes a canister of compressed, inert gas to inflate the bag. This gas is expanded at a very high rate through a heating process, that allows a small quantity of gas under a very high pressure to inflate the large passenger airbag. In 1997 the pressure in the canister is monitored by a pressure switch. If the pressure drops below the minimum pressure limit, the ACM will turn on the airbag warning lamp and set a diagnostic trouble code (DTC).
The Prowler utilizes two front impact sensors, located on each side of the battery and a safing sensor located in the ACM to control the deployment of the airbags. Diagnosis of the system is done through the Data Link Connector (DLC) located under and just to the left of the steering column.
The airbag lamp is located in the cluster. Whenever the ignition key is turned to the "run" position, the cluster illuminates the bulb for 7 seconds. This illumination is called bulb prove-out. After the 7 seconds, the bulb will normally extinguish The bulb will illuminate if the ACM senses a fault in the Airbag system and communicates this message to the cluster via the CCD bus. The cluster will also light the light if the ACM fails to communicate with it for 5 consecutive seconds. If for some reason the cluster illuminates the airbag lamp, it will keep the lamp illuminated for a minimum of 12 seconds. This lamp is not dimmable.
The ACM has two different voltage supply circuits. They are supplied through fuse #5 and fuse #9.
The ACM monitors critical input and output circuits within the airbag system, making sure they are operating correctly. Some circuits are tested continuously; others are checked only under certain circumstances. The ACM provides diagnostic information about the airbag system to the technician through the DRB via the CCD bus.
The deceleration or g-force resulting from the impact of a front-end collision causes the front sensors to close. The safing sensor is designed to close from much lower g-forces than the front sensors. As soon as one of the front impact sensors and the safing sensor are closed, an electrical charge is sent to the airbag module. This causes the inflator to be actuated, thus deploying the airbags. The total time from the closure of the sensors to deployment and deflation of the airbags is less than 1/10 of one second.
The ACM also contains an energy storage capacitor. This capacitor stores enough electrical energy to deploy the airbags for up to two minutes following a battery disconnect or failure. The purpose of the capacitor is to provide airbag deployment in a severe secondary impact if the initial impact has damaged or disconnected the battery, but was not severe enough to deploy the airbags. The AIRBAG warning lamp is the only point at which "symptoms" of a system malfunction can be observed by the customer.
REPLACE AIRBAG SYSTEM COMPONENTS ONLY WITH PARTS SPECIFIED IN THE CHRYSLER MOPAR PARTS CATALOG. SUBSTITUTE PARTS MAY APPEAR INTERCHANGEABLE, BUT INTERNAL DIFFERENCES MAY RESULT IN INFERIOR OCCUPANT PROTECTION. THE FASTENERS, SCREWS, AND BOLTS ORIGINALLY USED FOR THE AIRBAG SYSTEM COMPONENTS HAVE SPECIAL COATINGS AND ARE SPECIFICALLY DESIGNED FOR THE AIRBAG SYSTEM. THEY MUST NEVER BE REPLACED WITH ANY SUBSTITUTES. ANY TIME A NEW FASTENER IS NEEDED, REPLACE IT WITH THE CORRECT FASTENERS PROVIDED IN THE SERVICE PACKAGE OR SPECIFIED IN THE CHRYSLER MOPAR PARTS CATALOG.
Active Codes
An active trouble code indicates an on-going malfunction. This means the defect is there every time the ACM checks that circuit/function. It is impossible to erase an active code; active codes are automatically erased by the ACM when the reason for the code has been corrected.
Stored Codes
Airbag codes are continuously stored in the ACM's memory when the ignition is turned off with the exception of the Loss of Ignition Run Only code, which is an active code only.
A stored code indicates there was an active code present at some time. However, the code currently may not be present as an active code, although another active code could be.
When a trouble code occurs, the AIRBAG warning lamp illuminates for 12 seconds minimum (even if the problem existed for less than 12 seconds). The code is stored, along with the time in minutes that it was active, and the number of times the ignition has been cycled since the problem was last detected.
The minimum time shown for any code will be one minute, even if the code was actually present for less than one minute. Thus, the time shown for a code that was present for two minutes 13 seconds would be three minutes.
If a malfunction is detected, a diagnostic trouble code is stored and will remain stored as long as the malfunction exists. When and if the malfunction ceases to exist the code is stored and an ignition cycle count will be initiated for the code. If the ignition cycle count reaches 100 without reoccurrence of that same malfunction, that diagnostic trouble code is erased and that ignition cycle counter is reset to zero. If the malfunction reoccurs before the count reaches 100, then the ignition cycle counter will be reset and the diagnostic trouble code will continue to be a stored code.
If a malfunction is not active while performing a diagnostic test procedure, the active code diagnostic test will not locate the source of the problem. In this case, the stored code can indicate an area to inspect.
If no obvious problems are found, erase the stored code, and with the ignition "on", wiggle the wire harness and connectors, rotate the steering wheel from stop to stop. Recheck for codes periodically as you work through the system. This procedure may uncover a malfunction that is difficult to locate.
Airbag Diagnostic Trouble Codes
For the following codes, replace the airbag control module (ACM).
- Internal Diagnostics 1
- Internal Diagnostics 2
- Internal Diagnostics 3
- Internal Diagnostics 4
- Low Stored Energy Driver
- Low Stored Energy Passenger
- Safing Sensor Shorted
For these codes, refer to the appropriate diagnostic procedure
- Driver Squib Circuit Open
- Driver Squib Circuit Shorted
- Front Sensor Circuit Open
- Loss of Ignition Run Only
- No CCD Bus Communication
- No Cluster CCD Bus Message
- One Front Sensor Circuit Open
- Passenger Squib Circuit Open
- Passenger Squib Circuit Shorted
- Pressure Switch Circuit Open/Shorted
- Safing Sensor Open
- Two Front Sensor Circuit Open
- Warning Lamp Circuit Open
- Warning Lamp Circuit Shorted