Document ID# 1911787
2008 Chevrolet Corvette

Immobilizer Operation
This vehicle has a passive theft-deterrent system.

The system is automatically armed when the ignition mode transitions to off.

The immobilization system is disarmed when the ignition mode transitions to OFF/ACCESSORY or START and a valid transmitter is found in the vehicle.

You do not have to manually arm or disarm the system.

The security light comes on if there is a problem with arming or disarming the theft-deterrent system.

The system has one or more keyless access transmitters that are matched to an immobilizer control unit in the vehicle. Only a correctly matched keyless access transmitter starts the vehicle. The vehicle may not start if the keyless access transmitter is damaged.

If the engine does not start and the security light comes on, there may be a problem with the immobilizer system. Press the START button again.

If the vehicle does not start and the keyless access transmitter appears to be undamaged, try another keyless access transmitter. Or, place the transmitter in the transmitter pocket. See "NO FOBS DETECTED" under DIC Warnings and Messages for additional information. Check the fuse. See Fuses and Circuit Breakers .

If the engine still does not start with the other transmitter, the vehicle needs service.
If the engine does start, the first transmitter may be faulty. See your dealer/retailer who can service the theft-deterrent system and have a new keyless access transmitter programmed to the vehicle.

It is possible for the immobilizer system to learn new or replacement keyless access transmitters. Up to four keyless access transmitters can be programmed for the vehicle. To program additional transmitters, see "Matching transmitter(s) to Your Vehicle" under Keyless Access System Operation .

Do not leave the key or device that disarms or deactivates the theft deterrent system in the vehicle.

This device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions:

This device may not cause interference.
This device must accept any interference received, including interference that may cause undesired operation.

This device complies with RSS-210 of Industry Canada. Operation is subject to the following two conditions:

Changes or modifications to this system by other than an authorized service facility could void authorization to use this equipment.

Document ID# 1911419
2008 Chevrolet Corvette

Immobilizer Description and Operation
Immobilizer System
The immobilizer system is incorporated into the remote control door lock receiver (RCDLR). The immobilizer is provided in order to prevent the vehicle operation if an incorrect or unprogrammed keyless entry transmitter is used in an attempt to start the vehicle.
When the ignition button is pressed, the backup keyless entry antenna broadcasts a challenge to the transmitter. Both the RCDLR and the transmitter perform a calculation based on this challenge. The transmitter will transmit its calculation result to the RCDLR via radio frequency (RF).
If both calculations match, vehicle starting will be allowed. This is accomplished by the RCDLR sending a fuel enable message to the engine control module (ECM).

The design of the immobilizer system is to prevent vehicle theft by disabling the engine unless the correct transmitter is present when attempting to start the vehicle.
The system is similar in concept to conventional immobilizer system which use a normal vehicle key. The components of the immobilizer system are as follows:

• The start button

• The #1-#4 keyless entry transmitters

• The backup keyless entry antenna

• The body control module (BCM)

• The RCDLR

• The security indicator

• The ECM

Start Button
The start button is located at the right side of the steering column, on the instrument panel. The start button is used to start the vehicle engine, turn OFF the vehicle, put the vehicle in ACC mode, or put the vehicle in RUN mode.

The start button signals the body control module (BCM) to ground the Run/Crank control relay which will then feed power to the Crank relay in the under hood fuse block.
The BCM also simultaneously send a serial data message to the engine control module (ECM) to ground the starter enable relay to allow power to the starter solenoid and starter motor.

Keyless Entry Transmitters
The keyless entry transmitters are not only used to passively or actively lock and unlock the vehicle, they are also used to allow vehicle starting.
If the remote control door lock receiver (RCDLR) does not receive a valid RF response after the transmitter is challenged, the RCDLR will not send a fuel enable message to the engine control module (ECM).
If the RCDLR is unable to establish communication with the transmitter during an attempted engine start, the NO FOB DETECTED message will display on the driver information center (DIC).

When any one of the 4 allowable programmed key fobs are challenged by pressing the start button, they will passively send a RF signal to the RCDLR. The RCDLR will then send a serial data message to the engine control module (ECM) to enable engine starting.

Keyless Entry Antenna - Backup
The backup keyless entry antenna is located in the glove box area. It has a small pocket next to it where the transmitter can be inserted if the transmitter battery is dead, weak, or the RF signal is being interrupted.

The purpose of the backup keyless entry antenna is to send a low frequency RF challenge to a programmed transmitter within the interior of the vehicle when the start button is pressed. The backup keyless entry antenna is controlled by the remote control door lock receiver (RCDLR).

Body Control Module (BCM)
Important: The remote control door lock receiver (RCDLR) does not communicate on the GM LAN high speed bus. The RCDLR and the engine control module (ECM) use the BCM as a gateway in order to communicate.

The body control module is a multi-function module. The body control module (BCM) is used in the immobilizer system as a gateway for the RCDLR to send a fuel enable message to the ECM.

Remote Control Door Lock Receiver (RCDLR)
Important: The RCDLR does not communicate on the GM LAN high speed bus. The RCDLR and the engine control module (ECM) use the body control module (BCM) as a gateway in order to communicate.

The backup keyless entry antenna is controlled by the RCDLR. The RCDLR also controls three other low frequency antennas used for passive vehicle entry, but not for immobilizer operations. The RCDLR will send an AC voltage signal and provide ground to the backup keyless entry antenna when the ignition button is pressed.
This will enable the backup keyless entry antenna to send out a low frequency broadcast challenge to a transmitter. The RCDLR also has an internal radio frequency (RF) antenna to receive the transmitters passively or actively sent responses. The RCDLR is responsible for sending the fuel enable message to the ECM if all the requirements are met.

Security Indicator
The security indicator appears on the instrument cluster. If the security indicator flashes or is illuminated continuously during vehicle operation, a malfunction exists within the immobilizer system.
The security indicator is a dual purpose indicator. With the ignition OFF, the indicator it is controlled by the body control module (BCM) as a status indicator for the content theft deterrent system. With the ignition ON, it is controlled by the immobilizer system as a fault indicator.

Engine Control Module (ECM)
Important: The remote control door lock receiver (RCDLR) does not communicate on the GM LAN high speed bus. The RCDLR and the ECM use the body control module (BCM) as a gateway in order to communicate.

The ECM communicates with the BCM and the RCDLR over the serial data line. If the RCDLR receives a valid transmitter RF response, the RCDLR will send the fuel enable message to the ECM to enable the starting system. If the RCDLR does not receive a valid response from the transmitter, the RCDLR will send the fuel disable message, indicating to the ECM that vehicle starting should not be allowed. Additionally, if the fuel enable password received by the ECM does match the stored password, vehicle starting will be disabled.

Document ID# 1877846
2008 Chevrolet Corvette

DTC P1630
Diagnostic Instructions
• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor
DTC P1630: Theft Deterrent Learn Mode Active


Circuit/System Description
When replacing a remote control door lock receiver (RCDLR), the engine control module (ECM) must learn the new fuel enable password from the replacement RCDLR. If the ECM is replaced with a service replacement part, it is in a functional state to automatically learn the fuel enable password.

If the RCDLR is replaced, the ECM must be placed in learn mode so it can learn the new RCDLR password. This DTC indicates the ECM is in a functional state to learn the RCDLR fuel enable password.

Conditions for Running the DTC
The ECM is in learn mode.

Conditions for Setting the DTC
DTC P1630 will set any time the ECM enters learn mode.

Action Taken When the DTC Sets
The security indicator will illuminate.

Conditions for Clearing the DTC
• A current DTC will be cleared upon a successful engine start after exit of learn mode.

• A history DTC will be cleared after 100 malfunction-free ignition cycles.

Reference Information
Schematic Reference
Immobilizer Schematics

Connector End View Reference
Component Connector End Views

Description and Operation
Immobilizer Description and Operation

Electrical Information Reference

• Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs


Scan Tool Reference
Control Module References for Scan Tool Information

Circuit/System Verification
Perform the 10-Minute Immobilizer Relearn procedure. Refer to Programming Immobilizer System Components . The ECM should successfully complete the password learn and the vehicle should start.

⇒ If the ECM does not complete the learn or vehicle starting remains disabled, replace the ECM.

Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming

DTC P1631
Diagnostic Instructions
• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor
DTC P1631: Theft Deterrent Fuel Enable Signal Not Correct


Circuit/System Description
The remote control door lock receiver (RCDLR) sends the fuel enable password to the engine control module (ECM) via the serial data circuit. If the fuel enable password received from the RCDLR equals the fuel enable password stored in the ECM, the ECM will allow vehicle starting