Airbag System: Notes

WARNING: This page is about a different car, the 2004 Dodge Pickup and 2004 Dodge Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

The airbag system is designed to provide increased driver and passenger protection if the vehicle is involved in a front end or side collisions. The system is most effective when used in conjunction with the seat belt system.

On some models the ACM supports Seat Belt Tensioners, Passenger Airbag Off Switch, and others Impact Sensor. It may be necessary to use the DRBIII® to reconfigure the ACM to the vehicle equipment.

The airbag control module (ACM) is an electronic module that monitors the airbag system for proper operation, stores diagnostic trouble code (DTCs), controls the airbag warning lamp and contains the sensor and actuator that is responsible for driver, passenger, and curtain airbag deployment. The ACM is mounted on a special bracket that is fastened to the floor of the truck at the bottom of the instrument panel. It is located forward of the console. The ACM provides diagnostic information (DTCs) to the technician through the DRBIII® via the PCI bus. Some circuits are tested continuously; others are checked only under certain circumstances. The warning lamp is driven with messages relayed to the Electro/Mechanical Instrument Cluster (EMIC) from the ACM via the PCI bus.

The AIRBAG warning lamp is the only point at which "symptoms" of a system malfunction can be observed by the customer. Whenever the ignition key is turned to the "run" position, the airbag control module performs a lamp check by turning the AIRBAG warning lamp on for 6-8 seconds. If the lamp remains off, it means that the ACM has checked the system and found it to be free of discernible malfunctions. If the lamp remains on, there could be an active fault in the system or the circuit that operates the lamp may be shorted to ground. If the lamp comes on and stays on for a period longer than 6-8 seconds, then goes off, there is usually an intermittent problem in the system.

WARNING: THE AIRBAG CONTROL MODULE CONTAINS THE IMPACT SENSOR, WHICH ENABLES THE SYSTEM TO DEPLOY THE AIRBAG. 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. THEN 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 OR DEATH.

WARNING: 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.

The DR will have two Airbag Control Modules. Each ACM is specifically calibrated for one body type, light duty or heavy duty. To determine the body types the ACM monitors the PCI Bus for a message containing the complete VIN. The ACM uses the 6th digit of the VIN to identify the heavy duty or light duty vehicle. The 6th digit of the VIN will be a number 1 for light-duty vehicle and a 2, 3 or 4 for heavy-duty vehicle. If the PCI Bus VIN message 6th character matches the ACM body type, the VIN will be stored within 5.6 seconds after ignition on. After the VIN is stored, the ACM verifies PCI Bus VIN message within 2.6 seconds after the ignition is turned on.

If two valid matching PCI Bus VIN messages are not received within 5.6 seconds the ACM will set a Missing Original VIN DTC.

If the ACM and PCM module types, 6th character of the VIN, light-duty or heavy-duty do not match the Calibration Mismatch DTC will be set.

CAUTION: Therefore, the practice of exchanging (swapping) airbag control modules, instrument clusters, powertrain control modules and other electronic modules in this vehicle with those removed from another vehicle must always be avoided.