E 250 Van V8-7.3L DSL Turbo VIN F (1995)
Air Bag Control Module: Description and Operation
The air bag diagnostic monitor continually monitors all supplemental air bag restraint system components and wiring connections for possible faults in
the system. If the air bag diagnostic monitor detects a fault in the supplemental air bag restraint system when the ignition switch is in the RUN position, a
diagnostic trouble code will be displayed on the air bag indicator, located in the instrument cluster. Performing system diagnostics is the main purpose of
the air bag diagnostic monitor.
The air bag diagnostic monitor does not deploy the air bag in the event of a crash. The center and right rear air bag sensors are "hard wired" to the air
bag, therefore, the center and right rear front primary crash sensors and RH cowl side panel air bag safing sensor determine when to deploy the air bag.
FEATURES AND FUNCTIONS
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The air bag diagnostic monitor illuminates the air bag indicator for approximately six seconds when the ignition switch is in the RUN position and
then turns the indicator off. This shows that the air bag indicator is operational. If the air bag indicator does not illuminate or the indicator stays on
or flashes at any time, a fault has been detected by the air bag diagnostic monitor.
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Diagnostic trouble codes may not be displayed for approximately 30 seconds after the ignition switch is placed in the RUN position. This is the
amount of time the air bag diagnostic monitor requires to perform all tests and verify system faults, if present.
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Each diagnostic trouble code (a series of flashes and pauses of the air bag indicator) represents a two-digit number. Each diagnostic trouble code is
always displayed at least twice. For example, a diagnostic trouble code 32 is displayed as three flashes, followed by a one-second pause, then two
flashes, followed by a three-second pause.
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If a system fault is present and the air bag indicator is malfunctioning, an audible tone will be heard, indicating that system service is required. The
tone is a series of five sets of five beeps. This does not indicate a diagnostic trouble code 55. If the tone is heard, the air bag indicator is
inoperative and a system fault that requires service is present.
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If a fault exists that makes unwanted air bag deployment possible, the air bag diagnostic monitor has an internal thermal fuse that will blow (open)
automatically. This removes all power to the air bag deployment circuit.
CAUTION: The thermal fuse does not blow (open) because of excessive current flowing through it. DO NOT attempt to jumper out the thermal
fuse with a circuit breaker or any other type of fuse.
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The air bag indicator will flash the appropriate diagnostic trouble code to indicate the suspect circuit. If the indicator is malfunctioning the tone
will be heard.
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Diagnostic trouble codes are prioritized numerically so if two or more different 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.
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The air bag diagnostic monitor includes an internal backup power supply. This feature provides sufficient backup power to deploy the air bag in
the event the battery or battery cables are damaged in an accident before the center air bag and front air bag sensors close. The backup power
supply will deplete its stored energy approximately one minute after the positive battery cable is disconnected.
WARNING: THE BACKUP POWER SUPPLY ENERGY MUST BE DEPLETED BEFORE ANY AIR BAG COMPONENT SERVICE
IS PERFORMED. TO DEPLETE THE BACKUP POWER SUPPLY ENERGY, DISCONNECT THE BATTERY POSITIVE CABLE
AND WAIT ONE MINUTE.
