Airbag System
AIRBAG SYSTEMThe airbag system is designed to provide increased driver and passenger protection if the vehicle is involved in a front-end collision. The system is designed to be used in conjunction with the seat belt system. Currently, DaimlerChrysler Corporation uses two types of Airbag Control Modules (ACM).
Whenever the ignition key is turned to the "run" or "start" position, the airbag control module (ACM) performs a warning indicator check by turning the AIRBAG warning indicator on. The indicator stays lit for 6 to 8 seconds, then goes off. If the indicator remains off, it means the ACM has checked the system and found it to be free of discernable malfunctions.
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 DRBIII via the PCI bus.
The deceleration of g-forces resulting from the impact of a front-end collision causes the electronic sensor inside of the ACM to be triggered. This causes the inflators to be actuated, thus deploying the airbags. The total time between determining to deploy and deflation of the air bag is 1/10th of a second (100 ms).
2002 Jeep Wranglers (TJ) will be equipped with a passenger airbag ON/OFF switch. This switch has an ACM controlled LED that will light when the switch is in the "OFF" position.
Use the diagnostic tests to find the cause of any customer complaint regarding the AIRBAG warning indicator such as:
* Airbag warning indicator does not come on at all
* Airbag warning indicator stays on
Passenger Airbag ON-OFF Switch
The Passenger Airbag ON-OFF Switch allows the customer to turn the passenger airbag function ON or OFF. The OFF indicator will be illuminated whenever the switch is turned to the OFF position and for 2 seconds at ignition ON for an indicator bulb test. The switch assembly is mounted to the console in front of floor shifter to make the OFF indicator visible to both front seat occupants.
WARNING: ALWAYS CHECK THE PASSENGER AIRBAG ON-OFF SWITCH POSITION BEFORE DRIVING THE VEHICLE. A SWITCH IN THE WRONG POSITION INCREASES THE RISK OF SERIOUS INJURY OR DEATH IN A COLLISION.
To operate, insert the ignition key into the switch keyhole, push key in to release the internal plunger, and rotate to the desired switch position. The spring-loaded locking plunger prevents the user from leaving the key in the switch. The key will be automatically ejected when force is not applied. The ignition key is the only key or object that should ever be inserted into the switch.
NOTE: Do not turn the ON-OFF switch with the ignition ON.
The ACM continuously monitors the resistance of the Passenger Airbag ON-OFF Switch circuits to identify the switch position and provide circuit diagnostics. The ON-OFF switch ON position resistance is 175 to 190 ohms and the OFF position resistance is 820 to 870 ohms. If the ON-OFF switch circuits are open, shorted to ground or battery the ACM will set active and stored DTCs. Upon receiving a switch diagnostic trouble code the airbag warning indicator, in the instrument cluster, will be turned ON by the ACM. Whenever the airbag warning indicator is illuminated, the ACM should be the first module interrogated.
WARNING: IGNORING THE AIRBAG WARNING INDICATOR IN YOUR INSTRUMENT PANEL COULD MEAN THE PASSENGER AIRBAG ON-OFF SWITCH IS NOT FUNCTIONAL AND THE AIRBAG MAY DEPLOY IF AN IMPACT OCCURS. IF THE AIRBAG WARNING INDICATOR TURNS ON WHILE DRIVING, THE AIRBAG ON-OFF SWITCH SETTING WILL REMAIN FUNCTIONAL FOR THAT KEY CYCLE. IF THE AIRBAG WARNING INDICATOR COMES ON AGAIN AT THE NEXT KEY ON AND STAYS LIT FOR MORE THAN 6-8 SECONDS, THE ACM WILL DEFAULT TO PASSENGER AIRBAG ON.
Special Tools
Some airbag diagnostic test use special tools, 8310 and 8443 airbag load tool, for testing squib circuits. 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, curtain airbag, clockspring, or seat belt tensioner (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 DTC's. If the module reports NO ACTIVE DTC's the defective component 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 exists, diagnostic priority should be given to the active code(s).
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 using the DRBIII. If more than one code exists, diagnostic priority should be given to the active codes(s).
Active diagnostic trouble codes for the airbag system are not permanent and will change the moment the reason for the code is corrected. In certain test procedures, diagnostic trouble codes are used as a diagnostic tool.
Active Codes
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/function. It is impossible to erase an active code; active codes automatically erase themselves when the reason for the code has been corrected.
With the exception of the warning indicator trouble codes or malfunctions, when a malfunction is detected, the AIRBAG indicator remains lit for a minimum of 12 seconds or as long as the malfunction is present.
Stored Codes
Airbag codes are automatically stored in the ACM's memory as soon as the malfunction is detected. 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 indicator illuminates for 12 seconds minimum (even if the problem existed for less than 12 seconds). Stored codes display the time in minutes that the code was active, and the number of times the ignition has been cycled since the active code 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, for example, would be three minutes.
Maintain a safe distance from all Airbags while performing the following inspection. 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 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.