Buick Regal: Description and Operation

IMMOBILIZER DESCRIPTION AND OPERATION

Without BTM

The immobilizer system functions are provided by the Immobilizer Control Module, the Body Control Module (BCM) and the Engine Control Module (ECM), as well as any modules which store and report the environment identifier.

When an ignition key is inserted into the ignition lock cylinder and the ignition is turned ON, the transponder in the key is energized by the immobilizer coil surrounding the ignition lock cylinder. This immobilizer coil is part of the Immobilizer Control Module. The transponder transmits a signal that contains its unique value, which is received by the BCM through the Immobilizer Control Module. The BCM then compares this value to a value stored in memory. The BCM also monitors various control modules to determine if the stored environment identifiers match.

If both the environment identifier and the value received from the transponder match, the BCM will send the prerelease password via serial data to the ECM. If the encrypted code's unique value is incorrect or the environment identifier does not match, the BCM will send the fuel disable message to the ECM.

When the ECM receives the BCM prerelease password, the ECM will challenge the password. The ECM sends this challenge to the BCM via serial data. Both the ECM and BCM perform a calculation on this challenge. If the BCM calculated response to the challenge equals the calculation performed by the ECM, the ECM will allow vehicle starting.

The components of the immobilizer system are as follows:

• BCM
• ECM
• Immobilizer Control Module
• Ignition key
• Security indicator
• Various control modules which store and report the environment identifier

With BTM

The immobilizer system functions are provided by the Keyless Entry Control Module, the Remote Control Door Lock Receiver, the Immobilizer Control Module, the Body Control Module (BCM) and the Engine Control Module (ECM), as well as any control modules which store and report the environment identifier. The Keyless Entry Control Module uses low frequency antennas in three different locations on the vehicle to determine the location of the transmitter. Multiple antenna are used to ensure complete coverage of the vehicle interior and rear compartment.

When the vehicle ON/OFF switch is pressed, the low frequency antennas emit a challenge to the keyless entry transmitter. The transmitter receives this challenge and emits it's response as an RF message. The transmitter transmits a signal that contains its unique value, which is received by the BCM through the Remote Control Door Lock Receiver. The BCM then compares this value to a value stored in memory.

The BCM also monitors various control modules to determine if the stored environment identifiers match.

If both the environment identifier and the value received from the transponder match, the BCM will send the prerelease password via serial data to the ECM. If the encrypted code's unique value is incorrect or the environment identifier does not match, the BCM will send the fuel disable message to the ECM.

When the ECM receives the BCM prerelease password, the ECM will challenge the password. The ECM sends this challenge to the BCM via serial data. Both the ECM and BCM perform a calculation on this challenge. If the BCM calculated response to the challenge equals the calculation performed by the ECM, the ECM will allow vehicle starting.

If RF communication is interrupted, a "No Remote Detected" message will be displayed on the DIC. In these cases, the transmitter can be placed in the transmitter slot/slot. The Immobilizer Control Module is located in the immediate vicinity of the transmitter pocket/slot. Placing the transmitter in the pocket/slot will create a low powered coupling between the transmitter and Immobilizer Control Module, allowing communications to occur and enabling vehicle starting.

The components of the immobilizer system are as follows:

• BCM
• ECM
• Remote Control Door Lock Receiver
• Immobilizer Control Module
• Low frequency antenna
• Ignition key/Keyless entry transmitter
• Security indicator
• Various control modules which store and report the environment identifier

Body Control Module (BCM)

The immobilizer system is an integral part of the BCM and is controlled internally within the BCM. The BCM can learn up to 8 keys (transponder values).

The BCM uses the following inputs:

• Environment identifier exchange with various modules
• Encrypted code from the vehicle key, received by the Immobilizer Control Module
• Encrypted code from the vehicle key, received by the Remote Control Door Lock Receiver (with BTM)

The BCM uses the following outputs:

• Prerelease password communication with ECM
• Challenge/response with ECM

When a transponder value is received by the BCM, the BCM will compare this value to the learned key code stored in memory. The BCM then performs one of the following functions:

• If the encrypted code value matches the values stored in the BCM memory, the BCM will send the prerelease password to the ECM via serial data.
• If the encrypted code unique value does not match the value stored in the BCM, the BCM will send the start disable message to the ECM via serial data.
• If the BCM is unable to measure the ignition key encrypted code value, the BCM will not send any messages to the ECM.

Engine Control Module (ECM)

When the ECM receives the BCM prerelease password, the ECM will challenge the password. The ECM sends this challenge to the BCM via the serial data circuit. Both the ECM and BCM perform a calculation on this challenge. If the calculated response from the BCM equals the calculation performed by the ECM, the ECM will allow vehicle starting.

The ECM will disable vehicle starting if any of the following immobilization conditions occur:

• The prerelease password is invalid.
• The start disable password is sent by the BCM.
• No passwords are received. There is no communication with the BCM.
• The BCM calculated response to the challenge does not equal the calculation performed by the ECM.

Immobilizer Control Module

The Immobilizer Control Module contains an immobilizer coil which surrounds the ignition cylinder (without BTM) or is located near the transmitter pocket/slot (with BTM). The coil passively powers the transponder located in the ignition key. When powered, the key transmits its unique value to the Immobilizer Control Module, which is then relayed to the BCM via a LIN serial data circuit. The Immobilizer Control Module also receives B+ and ground from the BCM.

The Immobilizer Control Module is used to:

1. Learn keys
2. To start vehicle with or without RF interference
3. To start vehicle when key battery is dead

Keyless Entry Control Module (with BTM)

The Keyless Entry Control Module uses low frequency antennas in three different locations on the vehicle to determine the location of the transmitter. Multiple antenna are used to ensure complete coverage of the vehicle interior and rear compartment. The Keyless Entry Control Module monitors the ignition mode switch. When the ignition mode is changed, the Keyless Entry Control Module will command, or "ping", the low frequency antenna.

Low Frequency Antenna (with BTM)

When commanded, or "pinged", the low frequency antenna broadcast a challenge to the keyless entry transmitter. Because of the low power of the antenna, this challenge is only broadcast in an approximate three meter range of the antenna. Multiple antenna are used to ensure complete coverage of the vehicle interior and rear compartment.

Remote Control Door Lock Receiver (with BTM)

When the keyless entry transmitter is challenged by a low frequency antenna, it responds by emitting a response as an RF message. The transmitter transmits a signal that contains its unique value, which is received by the Remote Control Door Lock Receiver. The Remote Control Door Lock Receiver relays this information to the BCM via a discreet serial data circuit.

Ignition Key or Keyless Entry Transmitter

Each ignition key or keyless entry transmitter contains a transponder with a unique encrypted value. The transponder's encrypted value is fixed and unable to be changed. The immobilizer system uses the ignition key transponder value to determine if a valid ignition key is being used to start the vehicle.

Environment Identifier

Various modules throughout the vehicle learn a specific environment identifier during the module programming process. The environment identifier is learned by each individual module and matches the environment identifier stored in the BCM. Prior to starting after a battery disconnect, each of the modules which store a environment identifier will compare their identifier to that of the identifier stored in the BCM. If all the identifiers match, the engine starting process will continue. If the environment identifiers do not match, engine starting will be disabled.

Security Indicator

The BCM will command the Instrument Cluster to illuminate the security indicator when the ignition key is in the ON position to indicate a fault has occurred within the immobilizer system and when the engine starting is disabled.

REMOTE VEHICLE SPEED LIMITING DESCRIPTION AND OPERATION

Certain vehicles equipped with OnStar now have an additional feature that allows for remote limiting of the vehicle's speed. This OnStar feature is called Stolen Vehicle Slow-Down and is now part of the OnStar Stolen Vehicle Assistance service. This feature, when used in conjunction with local law enforcement and strict guidelines at the OnStar Call Center, will slow the vehicle by interacting with the engine control system.

When the engine control system receives a valid request from the OnStar telematics communications interface module, it will enter into a reduced engine power/vehicle speed limiting mode, which will decelerate the vehicle. Once the request is active the engine control module begins reducing engine torque to match requested vehicle speed and a REDUCED ENGINE POWER indication is displayed. No DTCs will be set during this process.

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