Supplemental Inflatable Restraint (SIR)

CIRCUIT DESCRIPTION
The center sensor assembly contains the diagnosis and memory circuits, safety circuit, DC-DC converter, 6 volt reserve power supply, arming sensor and passenger compartment sensor. When the center sensor assembly senses that the vehicle is involved in a frontal crash, it will close the arming sensor. If there are no DTCs stored in the diagnosis and memory circuits, the safety circuit will be closed, allowing voltage to be applied to the high side of the driver inflator module (D+ CKT) and passenger inflator module (P+ CKT). If the vehicle is involved in a deployment level frontal crash, the center sensor assembly will ground the low side of the driver inflator module (D- CKT) and passenger inflator module (P- CKT) through the passenger compartment sensor. When the center sensor assembly detects that the arming sensor and at least one other sensor (LH forward, RH forward or passenger compartment) is closed, it will deploy the air bags.

When system voltage is applied to the center sensor assembly, it will perform the "Primary Check" followed by the "Constant Check." When a fault is detected, the center sensor assembly will store a DTC and illuminate the "AIR BAG" indicator. When a DTC is stored, the safety circuit (inside the center sensor assembly) will open, preventing SRS operation. All faults must be repaired and all DTCs must be cleared before the safety circuit closes, allowing the SRS to function normally.

FAILURE CONDITIONS
DTC 31 will set if a fault occurs within the center sensor assembly.

ACTION TAKEN
The center sensor assembly will illuminate the "AIR BAG" indicator and will open the safety circuit preventing SRS operation.