Crown Victoria V8-281 4.6L SFI (1998)
Air Bag Electronic Crash Sensor: Description and Operation
Air Bag System Functions
Air Bag Indicator Lamp
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The air bag Electronic Crash Sensor (ECS) module illuminates the AIR BAG indicator for approximately six seconds when the ignition switch is
turned to RUN and then turns the AIR BAG indicator off. This indicates that the AIR BAG indicator is operational. If the AIR BAG indicator does
not illuminate at all, stays on continuously or flashes at any time, then a fault has been detected by the ECS.
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Lamp Fault Codes (LFCs), if present, will begin flashing approximately 30 seconds after the ignition switch has been turned to RUN. This is the
amount of time it takes the ECS to perform all tests and verify system faults, if present.
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LFCs are displayed as a series of flashes and pauses of the AIR BAG indicator. LFCs are two-digit numbers.
Example: An LFC 32 is displayed as follows:
flash flash flash - (two second pause) -
flash flash - (five second pause)...
flash flash flash - (two second pause) -
flash flash - (five second pause)...
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LFCs are prioritized numerically so that if two or more faults occur at the same time, the LFC with the highest priority will be displayed.
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After the LFC is displayed five times, the air bag indicator will illuminate continuously until the ignition switch is cycled.
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The ECS incorporates Non-Volatile Random Access Memory (NVRAM) to store Diagnostic Trouble Codes (DTCs) and retain them indefinitely.
The ECS will always display the highest priority DTC stored in NVRAM. DTCs may be cleared from the ECS after the fault conditions are
serviced. Refer to Retrieve/Clear Continuous DTCs. See: Air Bag Systems/Testing and Inspection/Reading and Clearing Diagnostic Trouble
Codes/Retrieving Diagnostic Trouble Codes
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If a system fault exists and the air bag warning indicator is not functioning, an audible chime will be heard indicating a need for service. The chime
is a series of five sets of five beeps. This does not indicate an LFC 55 or any other DTC. The air bag warning indicator must be serviced before
LFCs can be determined.
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The ECS includes an internal backup power supply. This feature provides sufficient backup power to deploy the air bags in the event that 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 one minute after the battery ground cable is disconnected.
WARNING: TO AVOID ACCIDENTAL DEPLOYMENT AND POSSIBLE PERSONAL INJURY, THE BACKUP POWER SUPPLY
MUST BE DEPLETED BEFORE REPAIRING OR REPLACING ANY AIR BAG SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
COMPONENTS. TO DEPLETE THE BACKUP POWER SUPPLY ENERGY, DISCONNECT THE BATTERY GROUND CABLE
AND WAIT ONE MINUTE. BE SURE TO DISCONNECT AUXILIARY BATTERIES AND POWER SUPPLIES (IF SO EQUIPPED).
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The ECS incorporates an internal safing sensor. Proper mounting of the ECS and bracket assembly is critical to the function and performance of
the air bag system.
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The ECS is non-serviceable and must be replaced as a unit in the event of failure.
