Air Bag Control Module: Description and Operation

Occupant Restraint Controller Location:

The Occupant Restraint Controller (ORC) is also sometimes referred to as the Airbag Control Module (ACM). The ORC is mounted on the tunnel floor pan, between the transmission shifter and parking brake.

The ORC contains a microprocessor, the impact sensing device, and energy storage capacitors. The microprocessor contains the airbag system logic. The airbag system logic includes On-Board Diagnostics (OBD) capability, and communicates with the instrument cluster circuitry on the Programmable Communication Interface (PCI) data bus to control the airbag indicator lamp.

The impact sensing device is located inside the ORC. The sensing device provides crash severity discrimination and confirmation of a crash. The ORC monitors the system to determine the system readiness. The ORC contains on-board diagnostics (OBD), and will illuminate the AIRBAG warning lamp on the cluster when a fault occurs. The warning indicator is illuminated for six to eight seconds every time the vehicle is started.

The microprocessor in the ORC monitors internal components and the airbag system electrical circuits to determine the system readiness. If the ORC detects a monitored system fault, it sends messages to the instrument cluster over the PCI data bus to turn ON the airbag warning lamp. A decision algorithm in the ORC microprocessor determines when the deceleration rate is severe enough to require air-bag system protection. When the appropriate conditions are met, the ORC sends an electrical signal to deploy the frontal airbags. The impact sensing device is an accelerometer that senses deceleration, which provides verification of the severity of an impact. The ORC is calibrated for the specific vehicle, and is only serviced as a unit. The ORC also contains an energy-storage capacitor. The purpose of the capacitor is to provide airbag system protection if the impact has damaged or disconnected the battery. The ORC cannot be repaired or adjusted, and if damaged or faulty, must be replaced.