F 250 2WD Super Duty V8-7.3L DSL Turbo VIN F (1999)
Air Bag Control Module: Description and Operation
The air bag Electronic Crash Sensor (ECS) module performs the following functions:
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signals the inflators to deploy the air bags in the event of a deployable crash.
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monitors the air bag Supplemental Restraint System (SRS) for faults.
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illuminates the air bag indicator if a fault is detected.
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flashes the air bag indicator to indicate the Lamp Fault Code (LFC) detected.
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communicates through the Data Link Connector (DLC) the current and historical DTCs.
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signals the Generic Electronic Module (GEM) to activate a chime if the air bag indicator is not available and another SRS fault is present.
NOTE: The safing sensor is internal to the ECS and is not serviced separately.
The ECS monitors the SRS for possible faults. If a fault is detected while the ignition switch is in the RUN position, the ECS will illuminate the air bag
indicator located in the instrument cluster. When the ignition is cycled (turned off and then turned on), the air bag indicator will flash the two-digit lamp
fault code (LFC). The air bag indicator will flash the LFC five times, then it will remain illuminated for the rest of the key cycle. The ECS will also
communicate the current and historical DTCs through the data link connector (DLC), using the New Generation STAR (NGS) Tester. If the air bag
indicator does not function, and the system detects a fault condition, the ECS will signal the GEM to activate an audible chime. The chime is a series of
five sets of five tone bursts. If the chime or buzzer is heard, the SRS and the air bag indicator requires service.
Lamp fault codes are prioritized. If two or more faults occur at the same time, the fault having the highest priority will be displayed first. After that fault
has been corrected, the next highest priority fault will be displayed.
The ECS includes an internal backup power supply. This feature provides sufficient backup power to deploy the air bags in the event the battery or
battery cables are damaged in a collision before the safing and air bag sensors close. The backup power supply will deplete its stored energy
approximately 1 minute after the battery ground cable is disconnected.
The ECS also employs a "keep-alive" period that allows the module to remain powered and active for approximately six minutes after switching the
ignition key from the RUN position to the OFF position. During this period, the module is performing backup power supply regulation and crash
discrimination while being completely capable of all deployment functions.
