Airbag System
IDENTIFICATION OF SYSTEMThe vehicle systems that are part of the "body" system are:
- airbag system
- instrument cluster
- vehicle communications
Airbag System
The airbag system is designed to provide increased driver and passenger protection if the vehicle is involved in a front-end collision. The system is most effective when used in conjunction with the seat belt system. Currently, Chrysler Corporation uses two types of airbags control modules (ACM).
The ASDM system is a mechanically-triggered system utilizing two front impact sensors and a sensor inside the module. The AECM is an electronically-triggered system that uses only its own internal electronic sensor to trigger the airbags. The TJ Body uses only the AECM system.
Whenever the ignition key is turned to the "run" or "start" position, the airbag control module (ACM) performs a lamp check by turning the AIRBAG warning lamp on. The lamp stays lit for 6 to 8 seconds, then goes off. If the lamp remains off, it means the ACM has checked the system and found it to be free of discernable malfunctions. The airbag system is monitored by the ACM.
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 AIRBAG warning lamp is the only point at which "symptoms" of a system malfunction can be observed by the customer. The seat belt warning lamp is used as a back-up for a failed airbag warning lamp. If at "ignition on" (when the airbag warning lamp should be activated for 7 seconds), the airbag lamp fails to come on for the 7 second bulb check, the seat belt warning lamp will flash on and off for 30 seconds after its 7 second bulb check and will perform as the airbag warning lamp.
The deceleration or g-force 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 airbag is 1/10th of a second.
Starting in 1998 some TJ's will be equipped with a passenger airbag disable switch (PADS). This switch has a led that will light when the switch is in the "OFF" position. While in the "OFF" position a circuit board inside the switch will simulate a passenger airbag to prevent the ACM from loging a DTC. However it is important that the ignition be in the "OFF" before moving the PADS to the "OFF" or "ON" position, otherwise the ACM may log a DTC and turn on the airbag warning lamp due to the momentary open the switch contacts.
Use the test procedures to find the cause of any customer complaint regarding the AIRBAG warning lamp such as:
- warning lamp does not come on at all
- warning lamp stays on
Airbag 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
to diagnose an individual code.
Always begin by reading the diagnostic trouble codes using the DRB. This procedure begins with AIRBAG TEST 1A - Identifying Airbag System Problems. This will direct you to the specific test(s) that must be performed. If more than one code exists, diagnostic priority should be given to the active code(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 by themselves when the reason for The code has been corrected.
With the exception of the warning lamp trouble codes or malfunctions, when a malfunction is detected, the AIRBAG lamp 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 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 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, for example, would be three minutes.
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.
Airbag Trouble Codes
The airbag control module may report any of the following diagnostic trouble codes.
For the following active or stored codes, replace the airbag control module (ACM) even if set intermittently:
- AECM Accelerometer
- AECM Output Driver
- AECM Stored Energy Logic
- AECM Stored Energy Driver
- AECM Stored Energy Passenger
- Internal Diagnostic 1
- Internal Diagnostic 2
- Internal Diagnostic 3
- Internal Diagnostic 4
- Safing Sensor Shorted
For these codes, refer to the appropriate diagnostic procedure:
- Driver Squib Circuit Open
- Passenger Squib Circuit Shorted
- Driver Squib Circuit Shorted
- Passenger Squib Circuit Shorted
- Loss of Ignition Run Only
- Either Squib Term Shorted to Battery
- Loss of Ignition to Run/Start
- Either Squib Term Shorted to Battery
- No Cluster CCD Bus Message
- Warning Lamp Circuit Open/Shorted
- No CCD Communication