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post #1 of 8 (permalink) Old 09-16-2012, 07:44 PM Thread Starter
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Engine Immobilizer

Hi, I was looking around for information in regarding the engine immobilizer on the internet and couldn't find anything. I searched with google and looked through the search on this forum but didn't come up with anything.

The problem I have is that the car won't start probably because of the engine immobilizer. I was wondering how you can bypass the engine immobilizer / fix it.

When I attempt to start the car, the engine immobilizer light flashes and the electronics of the car flashes along with it. The car then locks up. I have tried unlocking it with just the key, and unlocking it with the remote. I have tried locking and unlocking the car in multiple ways.

This problem happened when I tried to check the check engine light codes. After I checked the codes, I tried to delete the codes and restart the car. The engine light was still on when I tried to start the car and this issue arose.

Thank you for any advice people have for this!
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post #2 of 8 (permalink) Old 09-16-2012, 08:12 PM
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Probably need a re-learn now.

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post #3 of 8 (permalink) Old 09-16-2012, 08:22 PM Thread Starter
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Need a re-learn? Sorry I am not quite familiar with the terminology.
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post #4 of 8 (permalink) Old 09-16-2012, 08:32 PM
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Immobilizer Description and Operation
The vehicle theft deterrent (VTD) system functions are provided by the theft deterrent module (TDM). 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 TDM. The TDM then compares this value to a value stored in memory. This is the learned key code. If the value is correct, the TDM sends a random generated number to the transponder. This is called a challenge. Both the transponder and the TDM module perform a calculation on the challenge. If the calculations match, the TDM sends the start enable message 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 TDM will send the start disable message to the ECM via the serial data circuit. The components of the VTD system are as follows:

• TDM

• ECM

• Ignition key (Transponder)

• Ignition lock cylinder

• Security indicator

Theft Deterrent Module (TDM)
Vehicles with steering column mounted ignition switches have the exciter integral with the theft deterrent module (TDM), which is located within the steering column. The TDM can learn up to 10 keys (transponder values).

The TDM uses the following inputs: battery voltage, ignition switched voltage and ground circuit. The TDM uses the following outputs: password exchange with the engine control module (ECM), start enable/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 TDM. The TDM then compares this value to the learned key code stored in memory. If the value is correct, the TDM sends the challenge to the transponder. Both the transponder and the TDM perform a calculation on the challenge. The TDM then performs one of the following functions:

• If both the transponder value and the calculation to the challenge are correct, the TDM will send the start enable message to the ECM via the serial data circuit.

• If either the transponders unique value or the calculation to the challenge is incorrect, the TDM will send the start disable message to the ECM via the serial data circuit.

• If the TDM is unable to measure the ignition key transponder value for 1 second due to a damaged or missing pellet or a damaged exciter, the TDM will send the start disable message to the ECM via the serial data circuit.

Engine Control Module (ECM)
Important: On some vehicles, if the ECM is unable to communicate with the vehicle theft deterrent (VTD) system after the vehicle has started, the ECM will consider the VTD system to be malfunctioning. The ECM will enter a fail enable state and will command the security indicator to illuminate. When the ECM is in a fail enable state, the vehicle will NOT stall or stop running. If the ECM is in a fail enable state when the ignition is switched OFF, the ECM will remain fail enable until communications with the VTD system has been restored. When the ECM 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.

The engine control module (ECM) verifies that the message received from the TDM via the serial data circuit is valid. The ECM can learn only one start enable password. If the start enable message is valid, the ECM enables the starting and fuel delivery systems.

The ECM disables the starting and fuel delivery systems if any of the following conditions occur:

• The start enable message is invalid.

• The start disable message is sent by the TDM.

• No passwords are received--There is no communication with the TDM.

The Ignition Key (Transponder)
The ignition key for passkey III+ (PK3+) equipped vehicles is a typical looking ignition key with a transponder located in the plastic head of the key. The transponder value is fixed and unable to be changed. The vehicle theft deterrent (VTD) system uses the ignition key transponder value to determine if a valid ignition key is being used to start the vehicle. There are approximately 3 trillion possible transponder values. There are no visible electrical contacts. The keys may be identified by the plus in a circle symbol stamped into the steel shank of the key.

Ignition Lock Cylinder
The ignition lock cylinder is located on the steering column. The exciter coils surround the ignition lock cylinder such that they are very close to the head of the key which contains the transponder pellet.

If an ignition lock cylinder is replaced, the new ignition lock cylinder must be coded to match the mechanical coding of the PK3+ keys. When replacing only an ignition lock cylinder, no programming procedure is necessary to either the key or the vehicle theft deterrent (VTD) system if existing keys are being used. When replacing an ignition lock cylinder and new PK3+ keys are required, the new keys must be learned by the theft deterrent control module.

Security Indicator Operation
The theft deterrent module (TDM) can command the body control module (BCM) to illuminate the security indicator only when the ignition key is in the ON position. A flashing indicator indicates unauthorized operation. Under the following conditions the security indicator may be commanded to illuminate or flash:

Security Indicator Stays Illuminated and Engine Starts
If the TDM was unable to measure the ignition key transponder value or the engine control module (ECM) lost communication with the vehicle theft deterrent (VTD) system while the engine was last running, the indicator will remain illuminated during subsequent ignition cycles. This is to remind the driver that the VTD system will not be functioning until the problem is corrected.

Security Indicator Illuminates when Engine is Running
If the TDM is unable to measure the ignition key transponder value or the ECM loses communication with the TDM while the engine is running, the security indicator will be illuminated.

Security Indicator Illuminated and Engine Does Not Start
If the TDM was unable to measure the ignition key transponder value, the ECM has detected a problem with the VTD system, or the VTD system is in Learn Mode, the security indicator will be illuminated.

Security Indicator Flashes and Engine Does Not Start
The TDM has measured an incorrect transponder value, the calculation to the challenge is incorrect or the ECM has lost communication with the theft deterrent control module. The VTD system considers this a tamper condition. The security indicator will flash.

---------- Post added at 11:30 PM ---------- Previous post was at 11:26 PM ----------

Immobilizer System Component Programming (Except Canada)
10-Minute Immobilizer Relearn
This 10-minute relearn procedure will relearn the start enable password between the theft deterrent module (TDM) and the engine control module (ECM).

Connect a scan tool to the vehicle.
Turn ON the ignition, with the engine OFF.
Ensure that all power consuming devices are turned OFF on the vehicle.
With a scan tool, select Request Info. under Service Programming System and follow the scan tool on-screen instructions.
Disconnect the scan tool from the vehicle and connect the scan tool to a Techline Terminal with the current Service Programming System (SPS) software.
On the Techline Terminal, select Service Programming System and follow the Techline Terminal on-screen instructions. Ensure the correct programming selection is chose 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 for Powertrain System selection.
Disconnect the scan tool from the Techline Terminal and reconnect the scan tool to the vehicle.
With a master vehicle key, turn ON the ignition with the engine OFF.
With a scan tool, select Program ECU under Service Programming System.
At this point the scan tool must remain connected for the duration of the 10-minute relearn procedure.
Important:

• The scan tool may 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.
30-Minute Immobilizer Relearn

---------- Post added at 11:32 PM ---------- Previous post was at 11:30 PM ----------

If your from Canada the procedure is slightly different.

Immobilizer System Component Programming (Canada)
10-Minute Immobilizer Relearn
This 10-minute relearn procedure will relearn the start enable password between the theft deterrent module (TDM) and the engine control module (ECM).

Connect a scan tool to the vehicle.
Turn ON the ignition, with the engine OFF.
Ensure that all power consuming devices are turned OFF on the vehicle.
With a scan tool, select Request Info. under Service Programming System and follow the scan tool on-screen instructions.
Disconnect the scan tool from the vehicle and connect the scan tool to a Techline Terminal with the current Service Programming System (SPS) software.
On the Techline Terminal, select Service Programming System and follow the Techline Terminal on-screen instructions. Ensure the correct programming selection is chose 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 for Powertrain System selection.
Disconnect the scan tool from the Techline Terminal and reconnect the scan tool to the vehicle.
With a master vehicle key, turn ON the ignition with the engine OFF.
With a scan tool, select Program ECU under Service Programming System.
At this point the scan tool must remain connected for the duration of the 10-minute relearn procedure.
Important:

• The scan tool may 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.

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post #5 of 8 (permalink) Old 09-16-2012, 08:47 PM Thread Starter
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Thank you very much!
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post #6 of 8 (permalink) Old 09-16-2012, 08:51 PM
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You're very welcomed, hope it works out Okay for U.

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post #7 of 8 (permalink) Old 09-17-2012, 12:21 AM Thread Starter
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Thanks! Unfortunately, I haven't been able to solve my problem yet. I am not sure if I have diagnosed the problem properly. I am not able to start the car, which I thought was the fault of the immobilizer. However, When I do try to start the car the check engine light flashes repeatedly. The heads up display tells me to "check charge system."
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post #8 of 8 (permalink) Old 09-17-2012, 05:01 AM
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You might just have a bad battery cell. That will bring voltage down bellow 11 volts and your car won't start. Check your battery for 12+ volts.

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