RAM 2500 Van V8-5.2L VIN Y (1998)
Air Bag Control Module: Description and Operation
SYSTEM OPERATION
The Airbag Control Module (ACM) is secured to a bracket on the floor panel underneath the driver side front seat in the passenger compartment
of the vehicle. The ACM contains a microprocessor that contains the airbag system logic, the impact sensor, and an energy storage capacitor. The
ACM system logic includes On-Board Diagnostics (OBD) capability, and communicates with the instrument cluster circuitry on the Chrysler
Collision Detection (CCD) data bus to control the airbag indicator lamp.
The microprocessor in the ACM monitors the impact sensor signal and the airbag system electrical circuits to determine the system readiness. If
the ACM detects a monitored system fault, it sends messages to the instrument cluster on the CCD data bus to turn on the airbag indicator lamp. A
pre-programmed decision algorithm in the ACM microprocessor determines when the deceleration rate signaled by the impact sensor indicates an
impact that is severe enough to require airbag system protection. When the programmed conditions are met, the ACM sends an electrical signal to
deploy the air-bag system components.
Only one impact sensor is used in this airbag system. The impact sensor is an accelerometer that senses the rate of vehicle deceleration, which
provides verification of the direction and severity of an impact. The impact sensor is calibrated for the specific vehicle, and is only serviced as a
unit with the ACM.
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 or adjusted and, if damaged or faulty, it must be replaced.
