Air Bag Systems: Description and Operation

DESCRIPTION
The airbag system is designed to provide increased driver 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.

CONTROL MODULE
Currently, Chrysler Corporation uses two types of airbag control modules. 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 airbag. The 1997 Dodge Ram pickup uses the ASDM system.

OPERATION
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 that the ACM has checked the system and found it to be free of discernible 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.

SAFING SENSOR
The deceleration or g-force resulting from the impact of a front-end collision causes the safing sensor inside of the ACM to be closed. As soon as one front sensor and the safing sensor are closed, an electrical charge is sent to the airbag module. This causes the inflators to be actuated, thus deploying the airbag. The total time from the closure of the switches to deployment and deflation of the airbag is 1/10th of a second.

WARNING LAMP
The AIRBAG warning lamp is the only point at which "symptoms" of a system malfunction can be observed by the customer.

CIRCUIT OPERATION
Airbag Squib (Airbag Igniter)
Two circuits, R43 and R45, connect the ACM to the driver's side airbag squib (igniter) after passing through the clock spring connector. Circuit R43 connects to cavity 3 of the ACM 4 way connector; circuit R45 connects to cavity 4 of the ACM 4 way connector. R43 and R45 are a twisted pair of wires.