Engine immobilizer / theft deterrent system indicator light does not go off when key is inserted and engine fail to start when key is turned to start position even when key is held in the position for more than a minute and the accelerator pedal depressed.

Vehicle Theft Deterrent (VTD) Description and Operation
The vehicle theft deterrent (VTD) system functions are provided by the theft deterrent control module. When an ignition key is inserted into the ignition lock cylinder and the ignition is switched ON, the transponder embedded in the head of the key is energized by the exciter coils surrounding the ignition lock cylinder. The energized transponder transmits a signal that contains its unique value, which is received by the theft deterrent control module. The theft deterrent control module then compares this value to a value stored in memory, learned key code. If the value is correct the theft deterrent control module sends a random generated number to the transponder, this is called a challenge. Both the transponder and the theft deterrent control module perform a calculation on the challenge, if the calculations match the theft deterrent control module sends the fuel continue password via the serial data circuit to the Engine control module (ECM). If either the transponders unique value or the calculation to the challenge is incorrect the theft deterrent control module will send the fuel disable password to the ECM via the serial data circuit. The components of the VTD system are as follows:
• Theft deterrent control module
• Engine control module (ECM)
• Ignition key (Transponder)
• Ignition lock cylinder
• Security indicator
Theft Deterrent Control Module
Vehicles with steering column mounted ignition switches have the exciter integral with the theft deterrent control module which is located within the steering column. Vehicles with instrument panel mounted ignition switches have exciter modules separate from the theft deterrent control module with the vehicle wiring harness connecting the two. The theft deterrent control module for vehicles with instrument panel mounted ignition switches is located within the instrument panel. The theft deterrent control module can learn up to ten keys (transponder values).
The theft deterrent control module uses the following inputs, battery voltage, ignition switched voltage and ground circuit. The theft deterrent control module uses the following outputs, password exchange with the ECM, fuel continue/disable via the serial data circuit.
When an ignition key is inserted into the ignition lock cylinder and the ignition is switched ON, the transponder embedded in the head of the key is energized by the exciter coils surrounding the ignition lock cylinder. The energized transponder transmits a signal that contains its unique value, which is received by the theft deterrent control module. The theft deterrent control module then compares this value to a value stored in memory, learned key code. If the value is correct the theft deterrent control module sends a random generated number to the transponder, this is called a challenge. Both the transponder and the theft deterrent control module perform a calculation on the challenge. The theft deterrent control module then performs one of the following functions:
• If both the transponder value and the calculation to the challenge are correct, the theft deterrent control module will send the fuel continue password to the ECM via the serial data circuit.
• If either the transponders unique value or the calculation to the challenge is incorrect the theft deterrent control module will send the fuel disable password to the ECM via the serial data circuit.
• If the theft deterrent control module is unable to measure the ignition key transponder value for one second due to a damaged or missing pellet or a damaged exciter, the theft deterrent control module will send the fuel disable password to the ECM via the serial data circuit.
Important: On some vehicles, If the VTD system is unable to read the ignition key transponder value after the vehicle has started, the VTD system will consider itself malfunctioning. The VTD system will enter a fail enable state and will command the security indicator to illuminate. When the VTD system is in a fail enable state the vehicle will NOT stall or stop running. If the VTD system is in a fail enable state when the ignition is switched OFF, the VTD system will remain fail enable until it is able to read a learned ignition key transponder value. When the VTD system is in a fail enable state the VTD system is NOT active and the vehicle will start. This feature is NOT available on all GM vehicle lines.

In most cases the theft deterrent system in your 2007 Chevrolet Impala will reset itself in 10 minutes. You can also remove the fuse for 10 seconds and replace it to reset the system.

Dealer or mobile lock smith . unless you have a professional scan tool that can program keys . For about $1,500 you can buy a autel scanner . Immobilizer System Component Programming
10-Minute Immobilizer Relearn
This 10-minute relearn procedure will relearn the prerelease password and the challenge/response data between the theft deterrent module (TDM) and the engine control module (ECM).
Connect a scan tool to the vehicle in the pass-thru arrangement.
Turn ON the ignition, with the engine OFF.
Ensure that all power consuming devices are turned OFF on the vehicle.
On the Techline Terminal, select Service Programming System and follow the Techline Terminal on-screen instructions, using the Pass-Thru method. Ensure the correct programming selection is chosen based on component being replaced or programmed. For this procedure, go to the V.T.D. Vehicle Theft Deterrent Learn menu and choose the Vehicle Theft Deterrent Learn, ECM, or PK3 Replaced selection.
At this point the scan tool must remain connected for the duration of the 10-minute relearn procedure.
Important:
• The scan tool will initially display 12 Minutes. The first 2 minutes allow the scan tool to initialize the appropriate control module. The remaining 10 minutes is the relearn timer.
• On some vehicles the security indicator may be illuminated for the duration of the 10-minute relearn procedure.
Observe the scan tool, after approximately 10 minutes the scan tool will display "Programming Successful, Turn OFF Ignition". The vehicle is now ready to relearn the key information and/or the passwords on the next ignition switch transition from OFF to CRANK.
Turn OFF the ignition and wait 2 minutes.
With a master vehicle key, turn the ignition to the RUN position for 15 seconds, then start the vehicle. The TDM and ECM have now relearned the pre-release password and the challenge/response data.
With a scan tool, clear any DTCs.

STARTING DISABLED REMOVE KEY
Refer to Theft Systems Description and Operation in Theft Deterrent

STARTING DISABLED REMOVE KEY
The radio illuminates the STARTING DISABLED REMOVE KEY message when the VTD system has disabled the starting system. The radio receives a message from the theft deterrent control module via the serial data circuit requesting illumination.

Your best bet have it towed to a qualified repair shop .
The vehicle theft deterrent (VTD) system functions are provided by the theft deterrent control module. When an ignition key is inserted into the ignition lock cylinder and the ignition is switched ON, the transponder embedded in the head of the key is energized by the exciter coils surrounding the ignition lock cylinder. The energized transponder transmits a signal that contains its unique value, which is received by the theft deterrent control module. The theft deterrent control module then compares this value to a value stored in memory, learned key code. If the value is correct the theft deterrent control module sends a random generated number to the transponder, this is called a challenge. Both the transponder and the theft deterrent control module perform a calculation on the challenge, if the calculations match the theft deterrent control module sends the fuel continue password via the serial data circuit to the Engine control module (ECM). If either the transponders unique value or the calculation to the challenge is incorrect the theft deterrent control module will send the fuel disable password to the ECM via the serial data circuit. The components of the VTD system are as follows:
• Theft deterrent control module
• Engine control module (ECM)
• Ignition key (Transponder)
• Ignition lock cylinder
• Security indicator

Anti-theft system transceiver ?
Theft Deterrent System
The Theft Deterrent System on this vehicle is comprised of two separate systems, the Personal Automotive Security System (PASS-Key?® III) and the Content Theft Deterrent (CTD) system. These system are described and diagnosed separately within this section. For CTD operation, refer to Content Theft Deterrent (CTD) Description .
SECURITY Indicator The yellow indicator SECURITY on the instrument cluster is controlled by both the PASS-Key?® III system (VTD module) and the CTD system (RIM).
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PASS-Key?® III system, the VTD commands the instrument cluster to control the indicator only when the ignition switch is ON.

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CTD system, the RIM commands the instrument cluster to control the indicator only when the ignition switch is OFF.
PASS-Key?® III System The PASS-Key?® III system is designed to help prevent vehicle theft by disabling the engine unless an ignition key with a specific electrical value is used in the ignition lock cylinder. The PASS-Key?® III system operates independently of the CTD system. Protection is provided even if the CTD system is not armed. The components of the system are the ignition keys (black or gray), ignition lock cylinder, Theft Deterrent (VTD) module, Reader Exciter, Powertrain Control Module (PCM) and two starter relays (START 1 and 2) in the underhood fuse block.

Anti-theft system problem , possibility ! Do you have a security light blinking ? Security Indicator
The security indicator is located in the clock on the top of the instrument panel. The light emitting diode (LED) displays the immobilizer system status. The immobilizer contains the LED driver hardware for direct connection of the LED.
Vehicle Theft Deterrent (VTD) Operation
The immobilizer system design prevents vehicle theft by interrupting the engine operation. The immobilizer system prevents the vehicle from starting. The engine operating functions interrupt if the immobilizer system does not recognize the transponder identification code of the ignition key. The immobilizer system and the content theft deterrent system do not interact. The system includes the following components:
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The ignition key

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The column-mounted theft deterrent module with integrated antenna

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The transponder

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The engine control module (ECM

Have it checked for DTC'S - diagnostic trouble code's . I suspect the problem is with the tdm module or the ignition switch ???? Assuming will only get you into trouble . If the PCM - engine computer does not see the right coded meassage from the TDM it won't turn on the fuel injectors or it will cut them off in two seconds . .
Buick Security Systems 1998 Chevy is the same .
Ignition Key With Wrong Resistor Pellet Code is Used To Start Engine
The theft deterrent module performs one of the two following actions when you attempt to start the vehicle with a wrong ignition key:
• There are 15 PASS-Key® II resistance ranges. The PASS-Key® II resistance may be one of the 14 valid but incorrect PASS-Key® II resistance ranges. The theft deterrent module will perform the following actions when you attempt to start the vehicle (if the condition is present during an engine start attempt or for 1 second any time after the engine has started):
• Turns on the SECURITY indicator
• Sends a password to the PCM through the fuel enable signal circuit
• The password disables fuel delivery to the engine.
• Disables the theft deterrent relay, which disables the starter circuit
• Disables sampling of the PASS-Key® II resistance for 3 minutes
• The 3 minute time period is called the shut-down period.
• Disconnecting the battery will not clear the timer sequence. The timer sequence will resume when battery power is restored.
• Inserting the proper key during the vehicle shut-down period will not start the engine. The engine will not start until the shut-down period has elapsed.
• After the shut-down period, the engine will start if the correct ignition key resistor pellet is used.
• The PASS-Key® II resistance may be correct and allow the engine to start. Later during the same ignition cycle, the PASS-Key® II resistance may be one of the 14 valid but incorrect resistance ranges. The theft deterrent module will perform the following actions:
• Enters the fail-enable mode
• Turns ON the SECURITY indicator
• Sends a password to the PCM through the fuel enable signal circuit when more attempts to start the engine occur
• The password allows the fuel enable circuit to deliver fuel to the engine.
• Enables the theft deterrent relay, which also enables the starter circuit.

Ignition Key With Correct Resistor Pellet Code is Used To Start Engine
The theft deterrent module performs the following actions when the correct ignition key is used in order to start the vehicle:
• Enables the theft deterrent relay. The theft deterrent relay enables the starter unit.
• Sends a password to the Powertrain Control Module (PCM) through the fuel enable signal circuit. As a result, the PCM allows fuel delivery to the engine.


By pass theft system .
GM VATS Key Resistor Key Security Bypass

Hello Jaclyn... Your Camry has an "engine immobilizer" designed to prevent "hot-wire" starting incorporated into the anti-theft system...This was standard on the XLE, & an available option on the LE. When the battery cable came off the immobilizer lost it's memory & is not reckoning the chip in the key. Try locking and closing all the doors. Then unlock the drivers door with the key. Repeat this several times, also tap the brake & gas pedal. If this does not help the dealer will have to reset it by the vehicles VIN number.
I hope this information is helpful.

STARTING DISABLED REMOVE KEY
Refer to Theft Systems Description and Operation in Theft Deterrent

STARTING DISABLED REMOVE KEY
The radio illuminates the STARTING DISABLED REMOVE KEY message when the VTD system has disabled the starting system. The radio receives a message from the theft deterrent control module via the serial data circuit requesting illumination.

Your best bet ,take it to Cadillac dealer and have it checked . Could have DTC'S - diagnostic trouble codes
DTC B1015
DTC B1016
DTC B3031
DTC B3055
DTC B3060
DTC B3090
DTC B3935
DTC B3976
DTC P1629
DTC P1630
DTC P1631

The theft deterrent module or the insturment cluster or the ECM is not seeing correct info.
The vehicle theft deterrent (VTD) system functions are provided by the theft deterrent control module. When an ignition key is inserted into the ignition lock cylinder and the ignition is switched ON, the transponder embedded in the head of the key is energized by the exciter coils surrounding the ignition lock cylinder. The energized transponder transmits a signal that contains its unique value, which is received by the theft deterrent control module. The theft deterrent control module then compares this value to a value stored in memory, learned key code. If the value is correct the theft deterrent control module sends a random generated number to the transponder, this is called a challenge. Both the transponder and the theft deterrent control module perform a calculation on the challenge, if the calculations match the theft deterrent control module sends the fuel continue password via the serial data circuit to the Engine control module (ECM). If either the transponders unique value or the calculation to the challenge is incorrect the theft deterrent control module will send the fuel disable password to the ECM via the serial data circuit. The components of the VTD system are as follows:
• Theft deterrent control module
• Engine control module (ECM)
• Ignition key (Transponder)
• Ignition lock cylinder
• Security indicator

That's your immobilizer system light:
The Immobilizer System protects your car from theft. A properly coded master or valet key must be used in the ignition switch for the engine to start.
If an improperly coded key (or other device) is used, the engine’s fuel system is disabled.
When you turn the ignition switch to ON (II), the Immobilizer System indicator should come on for a few seconds, then go out. If the indicator starts to blink, it means the system does not recognize the coding of the key. Turn the ignition switch to LOCK (0), remove the key, reinsert it, and turn the switch to ON (II) again.
The system may not recognize your key’s coding if another immobilizer key or other metal object is near the ignition switch when you insert the key. To make sure the system recognizes the key code:
Do not keep other immobilizer keys on the same key ring.
Use a plastic or leather key fob, not metal.
Keep other keys away from your vehicle’s key and the ignition switch while trying to start the engine.
Do not attempt to alter this system or add other devices to it. Electrical problems could result that may make your car undriveable.
This indicator will also blink several times when you turn the ignition switch from ON (II) to ACCESSORY (I) or LOCK (0).
If the system repeatedly does not recognize the coding of your key, contact your Honda dealer.
If you have lost your key and you cannot start the engine, contact your Honda dealer.
Hope this lets you understand the light, and what should be happening.