Air Bag Control Module: Description and Operation

DESCRIPTION
The Airbag Control Module (ACM) contains the impact sensor, and a microprocessor that monitors the impact sensor and the airbag system electrical circuits to determine the system readiness. The ACM contains On-Board Diagnostics (OBD), and will send an airbag lamp-on message to the instrument cluster on the Chrysler Collision Detection (CCD) data bus to light the airbag indicator lamp in the instrument cluster when a monitored airbag system fault occurs.

OPERATION
The ACM also contains an energy-storage capacitor. This capacitor stores enough electrical energy to deploy the airbags for up to one second following a battery disconnect or failure during an impact. The purpose of the capacitor is to provide airbag system protection in a severe secondary impact, if the initial impact has damaged or disconnected the battery, but was not severe enough to deploy the airbags.

The ACM cannot be repaired and, if damaged or faulty, it must be replaced.

CIRCUIT OPERATION
Two circuits provide battery voltage to the Airbag Control Module (ACM); F14 and F23. Circuits F14 and F23 are connected to separate bus bars in the fuse block. Different circuits from the Power Distribution Center (PDC) and the ignition switch supply battery voltage to the fuse block bus bars.

Circuit F23 supplies battery voltage to the ACM only when the ignition switch is in the RUN position. Circuit F14 circuit powers the ACM when the ignition switch is in either the START or RUN position.

In either the START or RUN position, the ignition switch connects circuit A1 from fuse 7 in the PDC with circuit A21. Circuit A21 circuit supplies battery voltage to the fuse block bus bar that feeds circuit F14. Fuse 19 in the fuse block protects circuit F14. Circuit F14 connects to the ACM.

When the ignition switch is in the RUN position, it connects circuit A2 from fuse 2 in the PDC to circuit A22. Circuit A22 supplies battery voltage to the fuse block bus bar that feeds circuit F23. Fuse 1 in the fuse block protects circuit F23. Circuit F20 connects to the ACM.

The ACM is has an external dedicated ground, circuit Z6.