Mustang Cobra V8-281 4.6L DOHC VIN V MFI (1997)
Alarm System Transponder: Description and Operation
Anti-Theft System Operation
The passive antitheft system components function as follows:
THEFT indicator
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The passive anti-theft system utilizes the same (THEFT) indicator, (located in the instrument cluster) that the anti-theft alarm system (if equipped)
uses.
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The indicator provides system proveout and operating status to the customer or service technician.
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The active anti-theft alarm system uses the theft indicator when the ignition switch is turned OFF.
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When the ignition switch is turned to RUN/START the passive anti-theft system will activate the THEFT indicator signal ON for two seconds,
then OFF to indicate Key Code Received/Vehicle Enabled (programmed key).
Any other THEFT indicator illumination indicates a Passive Anti-theft System (PATS) concern:
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THEFT indicator ON two seconds, then OFF one second, then ON continuously indicates key code received/vehicle disabled (Assembly plant use
only, less than two keys programmed).
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THEFT indicator ON two seconds, then flash for one minute, then flash Fault Code 16 ten times indicates key code received I vehicle enabled or
disabled, no Powertrain Control Module (PCM) verification.
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If vehicle starts, PCM is not working with PATS control module.
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If vehicle does not start, the J 1850 Communication Network may need service.
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THEFT indicator flashes for one minute indicates no key code received. Causes include:
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damaged key
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non-encoded key
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wiring concern
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PATS module
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THEFT indicator flashes for 15 minutes indicates key code received/vehicle disabled (key not programmed).
Encoded Ignition Key
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When the vehicle ignition switch is placed into either RUN or START the control module initiates a key interrogation sequence.
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The PATS control module starts an interrogation period by supplying both power and the carrier signal to the transceiver to energize the ignition
key.
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After the energize period has expired, the key transmits its ID code to the transceiver module.
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This ignition key is much larger in size due to the electronics that are located in the head of the ignition key.
Transceiver
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The transceiver module is used to interface the PATS control module to the encoded ignition key.
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Sends power to the encoded key and receives the ignition key data signal.
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In turn, the transceiver sends the key code to the PATS control module which determines if the key being used is a properly coded key.
Passive Anti-Theft System Module
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The control module contains circuitry to interface to the vehicle electrical system, the transceiver module, the vehicle J1850 communications
network and the THEFT indicator located in the instrument cluster.
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The control module uses a microprocessor to control the system functions.
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The control module microprocessor stores the ignition key codes in Non-volatile Random Access Memory (NVRAM).
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The control module can be diagnosed through the data link connector.
Powertrain Control Module (PCM)
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The passive anti-theft system utilizes the engine management capabilities of the PCM to enable or disable the engine.
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The J1850 communications network is used to send and receive messages to and from the PCM.
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At each engine start sequence, the PCM allows fuel and spark until the engine is running.
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Within one second after engine start, the PCM must receive an enable signal from the anti-theft system control module or the engine is dis abled.
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If the passive anti-theft system control module recognizes a stored ignition key code and there is no J1850 communications network concern
preventing the PCM recognizing the start enable signal from the passive anti-theft system module, the engine will start and run.
Vehicle Disabling
The passive anti-theft system will be activated and will disable the vehicle from starting if any of the following conditions exist:
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damaged encoded key
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unprogrammed key
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non-encoded key (key has no electronics)
