Air Bag Systems: Description and Operation
The Sprinter Airbag System contains the following components:- Airbag Control Module (ACM)
- Airbag Warning Indicator (SRS)
- Driver Airbags
- Clockspring
- Passenger Airbag
- Driver Seat Belt Tensioners
- Passenger Seat Belt Tensioners
The Airbag Control Module (ACM) has five major functions: on-board diagnostics, determine the severity of impacts, squib deployment and Accident Response, K-Line communications. The ACM is secured to the floor under the Driver seat and receives power from the Fuse Block No. 1. Whenever the ignition key is turned to the run or start position, the ACM performs a system test. The ACM cannot be repaired or adjusted.
The microprocessor in the ACM monitors the internal and external airbag system electrical circuits to determine the system readiness. When monitored system is determine to be out of range, the ACM will set both active and stored diagnostic trouble codes (DTC). The ACM also contains an energy-storage capacitor. This capacitor stores enough electrical energy to deploy the front airbag components for two seconds following a battery disconnect or failure during an impact.
The Accelerometer in the ACM is used to sense the rate of vehicle deceleration, provide verification of the direction and severity of an impact. When the preprogrammed conditions are met, the ACM sends an electrical signal to deploy the appropriate front airbag system components and a deployment notification.
To provide an accident response notification, the ACM is hardwired to the Central Timer module (CTM) and Engine Control Module (ECM). When deployment occurs the ACM provides a 50 ms 10.0 volt pulse to the CTM and ECM. When the Accident Report notification signal is received the CTM unlocks the door locks and the ECM stalls the engine The Accident signal will set a DTC in the CTM and the door locks will not work until the DTC has been erased. The ECM will set a DTC if the Accident Report circuit is shorted to battery voltage. The ACM saves the deployment record and after three deployments the ACM must be replaced. The DRBIII(R) can be used to test the Accident Report Notification feature: select the SYSTEM TEST from the ACM main menu. Then select the Analog Crash Output System Test.
The ACM is hardwired to the Instrument Cluster (MIC) to control Warning Indicator (SRS indicator). When DTCs becomes activate, the ACM illuminates the Warning Indicator by pulling the indicator circuit low. The SRS indicator is the only point at which the customer can observe symptoms of a system malfunction.
As part of the system test the ACM illuminates the Warning Indicator on for 4.0 second bulb test. After the lamp check, if the indicator turns off, it means that the ACM has checked the system and found it to be free of discernible malfunctions.
NON-CRITICAL DTCs
If the lamp comes on and stays on for a period longer than 4.0 seconds (about 10.0 seconds) is usually a stored DTC (intermittent problem) in the system.
CRITICAL DTCs
DTCs that could lead to a condition where the safety devises may not deploy or incorrectly deploy. In the event of such a DTC, the safety of the vehicle occupants can no longer be guaranteed. If the lamp remains on, there could be an active DTC in the system. Some DTCs, Internal Module and squib DTCs, will keep the indicator illuminated even if the codes are no longer active.
ACM NOT CONFIGURED FOR PASSENGER AIRBAG AND TENSIONER
If after replacing the ACM the Airbag Warning Indicator flashes continuously the ACM must be configured for the Passenger Airbag and Tensioner. Select Miscellaneous from the ACM main menu and configure the Passenger Airbag Tensioner squibs.
WARNING:
- THE AIRBAG SYSTEM IS A SENSITIVE, COMPLEX ELECTROMECHANICAL UNIT. BEFORE ATTEMPTING TO DIAGNOSE OR SERVICE ANY AIRBAG SYSTEM OR RELATED STEERING WHEEL, STEERING COLUMN, OR INSTRUMENT PANEL COMPONENTS YOU MUST FIRST DISCONNECT AND ISOLATE THE BATTERY NEGATIVE (GROUND) CABLE. WAIT TWO MINUTES FOR THE SYSTEM CAPACITOR TO DISCHARGE BEFORE FURTHER SYSTEM SERVICE. THIS IS THE ONLY SURE WAY TO DISABLE THE AIRBAG SYSTEM. FAILURE TO DO THIS COULD RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY.
- TO AVOID PERSONAL INJURY OR DEATH, NEVER STRIKE OR KICK THE AIRBAG CONTROL MODULE, AS IT CAN DAMAGE THE IMPACT SENSOR OR AFFECT ITS CALIBRATION.
- IF AN AIRBAG CONTROL MODULE IS ACCIDENTALLY DROPPED DURING SERVICE, THE MODULE MUST BE SCRAPPED AND REPLACED WITH A NEW UNIT. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND PERSONAL INJURY OR DEATH.
DRIVER AIRBAG
The airbag protective trim cover is the most visible part of the driver side airbag system. The airbag is mounted directly to the steering wheel. Located under the trim cover are the airbag cushion and the airbag cushion supporting components.
When supplied with the proper electrical signal, the inflator discharged the gas directly into the cushion. The airbag cannot be repaired, and must be replaced if deployed or in any way damaged.
WARNING: THE DRIVER AIRBAG MODULE CONTAINS ARGON GAS PRESSURIZED TO OVER 17236.89 KPA (2500 PSI). DO NOT ATTEMPT TO DISMANTLE AN AIRBAG MODULE OR TAMPER WITH ITS INFLATOR. DO NOT PUNCTURE, INCINERATE, OR BRING INTO CONTACT WITH ELECTRICITY. DO NOT STORE AT TEMPERATURE EXCEEDING 93° C (200° F). REPLACE AIRBAG SYSTEM COMPONENTS ONLY WITH PARTS SPECIFIED IN THE CHRYSLER MOPAR PARTS CATALOG. SUBSTITUTE PARTS MAY APPEAR INTER-CHANGEABLE,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 MOPAR PARTS CATALOG. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND PERSONAL INJURY OR DEATH.
CLOCKSPRING
The clockspring is mounted on the steering column under the steering wheel. This assembly consists of a plastic housing which contains a flat, ribbon-like, electrically conductive tape that winds and unwinds with the steering wheel rotation. The clockspring is used to maintain a continuous electrical circuit between the instrument panel wiring and the driver airbag and the horn. The clockspring must be properly centered when it is reinstalled on the steering column following any service procedure, or it could be damaged. The clockspring cannot be repaired and it must be replaced.
PASSENGER AIRBAG
The Passenger Airbag is optional equipment. When supplied with the proper electrical signal the passenger airbag inflator discharges the gas directly into the cushion. The airbag module cannot be repaired, and must be replaced if deployed or in any way damaged.
WARNING: THE PASSENGER AIRBAG MODULE CONTAINS ARGON GAS PRESSURIZED TO 17236.89 KPA (2500 PSI). DO NOT ATTEMPT TO DISMANTLE AN AIRBAG MODULE OR TAMPER WITH ITS INFLATOR. DO NOT PUNCTURE, INCINERATE, OR BRING INTO CONTACT WITH ELECTRICITY. DO NOT STORE AT TEMPERATURE EXCEEDING 93° C (200° F). REPLACE AIRBAG SYSTEM COMPONENTS ONLY WITH PARTS SPECIFIED IN THE MOPAR PARTS CATALOG. SUBSTITUTE PARTS MAY APPEAR INTER-CHANGEABLE, 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 MOPAR PARTS CATALOG. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND PERSONAL INJURY OR DEATH.
SEAT BELT TENSIONERS
Front seat belt systems incorporate a Driver and optional Passenger Seat Belt Tensioner Retractors. At the onset of an impact event each tensioner uses a pyrotechnic device, which is triggered simultaneously with the front airbags, to rapidly retract the seat belts. With the slack removed, the occupant's forward motion in an impact will be reduced as will the likelihood of contacting interior components. After an impact that deploys the airbag, the seat belt tensioner assembly must be replaced. The ACM module monitors the Seat Belt Tensioners circuit resistance and reports active and stored DTCs if any problem is found. Follow all of the safety procedures when servicing tensioner.
SPECIAL TOOLS
Airbag load tools 8310 and 8443 are used in some airbag diagnostic test. The load tools contain fixed resistive loads, jumpers and adapters. The fixed loads are connected to cables and mounted in a storage case. The cables can be directly connected to some airbag system connectors. Jumpers are used to convert the load tool cable connectors to the other airbag system connectors. The adapters are connected to the module harness connector to open shorting clips and protect the connector terminal during testing. When using the load tool follow all of the safety procedures in the service information for disconnecting airbag system components. Inspect the wiring, connector and terminals for damage or misalignment. Substitute the airbag load tool in place of a Driver or Passenger Airbag, seat belt tensioner, clockspring (use a jumper if needed). Then follow all of the safety procedures in the service information for connecting airbag system components. Read the module active DTCs. If the module reports NO ACTIVE DTCs the defective components has been removed from the system and should be replaced. If the DTC is still active, continue this process until all components in the circuit have been tested. Then disconnect the module connector and connect the matching adapter to the module connector. With all airbags disconnected and the adapter installed the squib wiring can be tested for open and shorted conditions.
DIAGNOSTIC TROUBLE CODES
Airbag diagnostic trouble codes consist of active and stored codes. If more than one code exists, diagnostic priority should be given to the active codes. Each diagnostic trouble code is diagnosed by following a specific testing procedure. The diagnostic test procedures contain step-by-step instructions for determining the cause of the trouble codes. It is not necessary to perform all of the tests in this book to diagnose an individual code. Always begin by reading the diagnostic trouble codes with the DRBIII(R). This will direct you to the specific test(s) that must be performed. In certain test procedures, diagnostic trouble codes are used as a diagnostic tool.
ACTIVE CODES
If the lamp remains on, there could be an active DTC in the system. The code becomes active as soon as the malfunction is detected or key-on, whichever occurs first. An active trouble code indicates an on-going malfunction. This means that the defect is currently there every time the airbag control module checks that circuit or component. Some DTCs, Internal Module and squib DTCs, will keep the indicator illuminated even if they are no longer active. If the lamp is on and no active codes are present, cycling the ignition switch off and then on will refresh the lamp state. It is impossible to erase an active code.
STORED CODES
Airbag codes are automatically stored in the ACM's memory as soon as the malfunction is detected. A stored code indicates there was an active code present at some time. Stored diagnostic trouble code will remain stored until erased by the DRB. 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. Maintain a safe distance from all airbags while performing the following inspection. If no obvious problems are found, erase stored codes, 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.