Air Bag Control Module: Description and Operation

The ACM/Air Bag System Diagnostic Module (ASDM) contains safing sensor and energy reserve capacitor, while the ACM/Air Bag Electronic Control Module (AECM) contains impact sensor and energy reserve capacitor. The ACM monitors system to determine system readiness. The ACM will store sufficient energy to deploy air bag for two minutes after battery has been disconnected. The ACM contains an on board diagnostics function that will illuminate air bag warning lamp when a system fault occurs.

CIRCUIT OPERATION
Two different circuits supply battery voltage from the junction block to the Airbag Control Module (ACM), they are F14 and F23. The F14 and F23 circuits are connected to separate bus bars internal to the junction block. Different circuits from the Power Distribution Center (PDC) and the ignition switch supply battery voltage to the junction block bus bars.

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

A bus bar internal to the ignition switch connects the A1 circuit from the PDC to the A21 circuit when the switch is in either the START or RUN position. The A21 circuit supplies battery voltage to the junction block bus bar that feeds the F14 circuit. A 20 Amp fuse in the PDC, cavity A, protects the A1 and A21 circuits. A 10 Amp fuse in cavity 19 of the junction block protects the F14 circuit.

When the ignition switch is in the RUN position, it connects the A2 circuit from the PDC to the A22 circuit. The A22 circuit supplies battery voltage to the junction block bus bar that feeds the F23 circuit. A 40 Amp fuse in cavity J of the PDC protects the A2 and A22 circuits. A 10 Amp fuse in cavity 7 of the junction block protects the F23 circuit.

The ACM has a case ground, and an external dedicated ground, circuit Z2. The dedicated ground connects to the ACM bracket.