BCM - wo im Tahoe

Bj.? Motor? Modell?

Servus.
Soviel ich weiß ist da ein "Modul", "Antenne" im Bereich hinter der Tachoeinheit.

Was haste vor ? Willste die Wegfahrsperre killen ?

Harry

z.B.

Hast PM

Body Control System Description and Operation
BCM Functions
The Body Control Module (BCM) performs multiple body control functions. The BCM can control devices directly connected to its outputs based on input information. The BCM evaluates this information and controls certain body control systems by commanding outputs on or off. The BCM control inputs can be:

Sensors and switches that are directly connected to the BCM
Class 2 serial data received from other control modules connected to the class 2 serial data link.
The BCM is also capable of controlling other vehicle systems that are not directly wired to the BCM. The BCM does this by sending specific messages on the class 2 serial data link. The control module capable of performing the required function will respond to the BCM message.

The BCM controls these functions:

Audible warnings, refer to Audible Warnings Description and Operation in Instrument Panel, Gages and Console
Automatic door locks, refer to Power Door Locks Description and Operation in Doors
Automatic headlamp control, refer to Exterior Lighting Systems Description and Operation in Lighting Systems
Interior lighting, refer to Interior Lighting Systems Description and Operation in Lighting Systems
Keyless entry (AUO option), refer to Keyless Entry System Description and Operation in Keyless Entry.
Passlock theft deterrent, refer to Vehicle Theft Deterrent (VTD) Description and Operation in Theft Deterrent.
Retained Accessory Power (RAP), refer to Retained Accessory Power (RAP) Description and Operation in Retained Accessory Power
Serial Data Power Mode
On vehicles that have several control modules connected by serial data circuits, one module is the power mode master (PMM). On this vehicle the PMM is the Body Control Module (BCM). The BCM receives 2 signals/circuits from the ignition switch. These are the Ignition 1 and Ignition 3 signals/circuits.

To determine the correct power mode the BCM uses:

The state of these signals/circuits, either switch closed (B+ = 1) or switch open (open = 0)
The status of the engine run flag.
The chart indicates the modes detected and transmitted by the BCM:

Correct Ignition Switch Inputs Ignition Key Position
Power Mode Parameter
Engine Run Flag Serial Data
Sampled Ignition Signal State

Ignition 1
Ignition 3

Off
Off-Awake
0
0
0

Unlock
Off-Awake
0
0
0

Run
Run
0
1
1

Crank
Crank
0
1
0

Accessory
Off-Awake
0
0
0

Run
Run
1
1
1

Fail-safe Operation
Since the operation of the vehicle systems depends on the power mode, there is a fail-safe plan in place should the BCM fail to send a power mode message. The fail-safe plan covers modules with discrete ignition signal inputs as well as those modules using exclusively serial data control of power mode.

Serial Data Messages
The modules that depend exclusively on serial data messages for power modes stay in the state dictated by the last valid BCM message until they receive the engine status from the PCM. If the BCM fails, the modules monitor the serial data circuit for the engine run flag serial data. If the engine run flag serial data is true, indicating that the engine is running, the modules fail-safe to "Run". In this state the modules and their subsystems can support all operator requirements. If the engine run flag serial data is false, indicating that the engine is not running, the modules fail-safe to "OFF-AWAKE". In this state the modules are constantly checking for a change status message on the serial data circuits and can respond to both local inputs and serial data inputs from other modules on the vehicle.

Discrete Ignition Signals
Those modules that have discrete ignition signal inputs also remain in the state dictated by the last valid BCM message received on the serial data circuits. They then check the state of their discrete ignition input to determine the current valid state. If the discrete ignition input is active, B+, the modules will fail-safe to the "RUN" power mode. If the discrete ignition input is not active, open or 0 voltage, the modules will fail-safe to "OFF-AWAKE". In this state the modules are constantly checking for a change status message on the serial data circuits and can respond to both local inputs and serial data inputs from other modules on the vehicle.

Vehicle Theft Deterrent (VTD) Description and Operation
Passlock™ System
The theft deterrent system has been incorporated into the body control module (BCM). The theft deterrent is provided in order to prevent the vehicle operation if the correct key is not used in order to start the vehicle. The ignition key turns the lock cylinder. The cylinder rotation produces an analog voltage code in the Passlock™ sensor. This voltage code is received by the BCM. The BCM compares the voltage code to the previously learned voltage code. If the codes match, a class 2 message is sent from the BCM to the powertrain control module (PCM)/vehicle control module (VCM). The message enables the fuel injectors.

The design of the Passlock™ system is to prevent vehicle theft by disabling the engine unless the ignition lock cylinder rotates properly by engaging the correct ignition key. The system is similar in concept to the PASS-Key® system. However, the Passlock™ system eliminates the need for a key mounted resistor pellet. The components of the Passlock™ system are as follows:

The ignition lock cylinder
The ignition switch
The Passlock™ sensor
The Body control module (BCM)
The security telltale
The vehicle/powertrain control module (VCM/PCM)
Ignition Lock Cylinder and Housing
The ignition lock cylinder is located at the upper right side of the steering column. The Passlock™ sensor is in the steering column. The Passlock™ sensor is separate from the key and lock cylinder. The key and the lock cylinder work together in order to determine if the proper ignition key was used to start the vehicle.

In the event of an open Class 2 serial data line between the BCM and the VCM/PCM, the vehicle will become fail-enabled if the VCM/PCM has already received the password from the BCM for that ignition cycle, the engine is running. In this event, the following conditions occur:

The security telltale will be ON continuously.
The VCM/PCM will become fail-enabled for future ignition cycles.
If a failure in the Class 2 serial data line occurs before the ignition cycle, when the VCM/PCM is not fail-enabled, the following conditions occur:

The VCM/PCM will never receive a valid password in order to enable the fuel injectors.
The vehicle will not start.
Ignition Switch
The lock cylinder and the visible key insert portion of the ignition switch are located at the upper right side of the steering column. The electrical switching portion of the assembly is separate from the key and lock cylinder. The electrical switch portion is hidden inside the steering column. The electrical switch portion and the key and lock cylinder synchronize and work in conjunction through the action of the mechanical assembly between the 2 parts.

Passlock™ Sensor
The Passlock™ sensor is inside the ignition cylinder lock housing. The Passlock™ sensor contains 2 hall effect sensors. The tamper hall effect sensor is on the top. The security hall effect sensor is under the tamper hall effect sensor. Both of the hall effect sensors monitor the magnet of the lock cylinder through an opening. The tamper hall effect sensor is physically placed on top of the security hall effect sensor. This arrangement enables the tamper hall effect sensor to engage first if an intruder attempts to bypass the Passlock™ sensor by placing a large magnet around that area of the steering column. There is a tamper resistor inside the Passlock™ sensor in order to help prevent tamper to the system. Passlock™ equipped vehicles have a selection of 10 different security resistors ranging from 0.5K ohms up to 13.6K ohms. Installing one of the security resistors inside the Passlock™ sensor will generate a unique Passlock™ code. All 10 combinations of the Passlock™ sensor have the same part number. However, you cannot simply replace the Passlock™ sensor and expect the system to operate properly. Always start by performing the Diagnostic System Check first and following the instructions.

Body Control Module
The Body Control Module (BCM) contains the theft deterrent system logic. The BCM reads the Passlock™ data from the Passlock™ sensor. If the Passlock™ data is correct, the BCM will pass theft. The BCM will then transmit the fuel continue password to the VCM/PCM.

During the tamper mode the vehicle may start. The vehicle will then stall. If the BCM receives the wrong Passlock™ data, the VTD will immediately go into the tamper mode. The tamper mode will lock-out the vehicle fuel injectors for 10 minutes. The SECURITY indicator will flash while the VTD is in the tamper mode.

If the Passlock™ sensor sends a correct password to the BCM when the ignition is in the ON position, the BCM will send a fuel enable signal to the VCM/PCM. The VCM/PCM will not disable the fuel due to any BCM message for the remainder of the ignition cycle.

SECURITY Telltale
The SECURITY telltale appears on the message center inside the instrument cluster. If the SECURITY telltale flashes or if the SECURITY telltale lights continuously during the vehicle operation, refer to the system diagnosis.

Vehicle/Powertrain Control Module
The VCM/PCM communicates with the BCM over the Class 2 serial data line. When the BCM determines a no start condition, it sends a Class 2 serial data password to the VCM/PCM in order to disable the fuel injection system. If the BCM receives the expected voltage from the Passlock™ sensor, the BCM sends a class 2 serial data password to the VCM/PCM in order to enable the fuel injection system. The VCM/PCM then allows the vehicle to start correctly. If the Class 2 serial data password from the BCM to the VCM/PCM is not within the Vehicle Security Status Message, the fuel injectors will shut OFF during a start attempt. The SECURITY telltale will be illuminated for 10 minutes. If the VCM/PCM does not receive the same password from the BCM as the last learned one, the vehicle will start and then stalls due to the Fuel Lockout.

Fuel Lockout Cycle
The Passlock™ system has a lockout cycle of approximately 10 minutes. Once the vehicle is in the lockout cycle, the vehicle remains in the lockout cycle for 10 minutes, even if the ignition switch is turned from the RUN position to the OFF position.

The Passlock™ system uses the lockout cycle in order to synchronize all of the Passlock™ components when any Passlock™ related part is changed. The Passlock™ system requires 3 consecutive lockout cycles in order to complete the 30 minute learn procedure for a changed component.

Changing the Passlock™ Components
The design of the Passlock™ system is to prevent theft even if the various theft deterrent parts change. The parts that can no longer be changed without the possibility of going into a tamper mode are:

The Passlock™ sensor
The BCM
The VCM/PCM
If you replace any of these parts the vehicle may start and stall for 10 minutes. This is the long tamper mode. If this occurs, the system must go through a long tamper mode cycle. During this time the SECURITY telltale will be flashing for the full 10 minutes and the DTC B3031 will be set. The BCM and the VCM/PCM require the full 10 minutes in order to complete a learn cycle. The ignition switch must remain in the RUN position until the SECURITY telltale stops flashing. You will need to repeat the cycle if the ignition switch does not remain in the RUN position. When replacing any of the above parts it is recommended to perform the Programming Theft Deterrent System Components procedure.

The design of the Passlock™ system is to prevent the vehicle operation if the proper ignition key is not used in order to start the vehicle. The mechanical key, in normal operation, will turn the ignition lock cylinder. The Passlock™ sensor monitoring the position of the lock cylinder will relay the Passlock™ data to the body control module (BCM). The BCM will determine the validity of the Passlock™ data. The BCM will send a fuel continue password to the vehicle/powertrain control module (VCM/PCM). When the VCM/PCM receives the correct password the VCM/PCM allows the fuel injectors to operate normally. The Passlock™ system requires the VCM/PCM and the BCM to communicate the various functions in order to operate. These functions transmit over the class 2 serial data line. For an explanation of the class 2 serial data description and operation, refer to Data Link Communications Description and Operation in Data Link Communications.

Body Control Module Replacement

Caution
Before servicing any electrical component, the ignition key must be in the OFF or LOCK position and all electrical loads must be OFF, unless instructed otherwise in these procedures. If a tool or equipment could easily come in contact with a live exposed electrical terminal, also disconnect the negative battery cable. Failure to follow these precautions may cause personal injury and/or damage to the vehicle or its components.

1.Disconnect the negative battery cable(s).
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2.Remove the knee bolster. Refer to Knee Bolster Replacement .
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3.Disconnect the brown connector.
4.Disconnect all other connectors (1).
5.Remove the BCM from the sliding bracket

Powertrain Control Module (PCM) Replacement
Service of the powertrain control module (PCM) should consist of either replacement of the PCM or electrically erasable programmable read only memory (EEPROM) programming. If diagnostic procedures call for PCM replacement, inspect the replacement PCM to ensure that the correct part PCM is being used.

Important
To prevent internal PCM damage, the ignition must be OFF when disconnecting or reconnecting power to the PCM. For example, when working with a battery cable, PCM pigtail, PCM fuse, or jumper cables.
Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM module connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion into the PCM.
The replacement PCM will not be programmed. DTC P0601 and P0602 indicate the EEPROM is not programmed or has malfunctioned. The following MUST be performed anytime the PCM is replaced:
Programming of the EEPROM
The PCM Password Learn procedure.
The Idle Learn Procedure .
The Crankshaft Position System Variation Learn Procedure .
Resetting the engine oil life monitor .
The Functional Check
The following must be performed anytime the PCM is disconnected, loses power, or is reprogrammed:
The Idle Learn Procedure .
The Functional Check

Removal Procedure

Important
It is necessary to record the remaining engine oil life. If the replacement module is not programed with the remaining engine oil life, the engine oil life will default to 100%. If the replacement module is not programmed with the remaining engine oil life, the engine oil will need to be changed at 5000 km (3,000 mi) from the last engine oil change.

1.Using a scan tool, retrieve the percentage of remaining engine oil. Record the remaining engine oil life.
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2.Release the PCM cover mounting holes (1, 5) away from the mounting tabs on the PCM mounting bracket.
3.Release the PCM cover (8) from the mounting bracket.
4.Remove the PCM cover.

Notice
Do not touch the connector pins or soldered components on the circuit board in order to prevent possible electrostatic discharge (ESD) damage to the PCM.

Notice
In order to prevent internal damage to the PCM, the ignition must be OFF when disconnecting or reconnecting the PCM connector.

5.Disconnect the PCM harness connectors (6).
6.Release the spring latch (2) from the PCM.
7.Release the PCM mounting tabs (3) from the PCM.
8.Remove the PCM (4) from the engine compartment.

Powertrain Control Module (PCM) Programming On-Board
Before Programming a Control Module

Important
DO NOT program a control module unless you are directed by a service procedure or you are directed by a General Motors Corporation service bulletin. Programming a control module at any other time will not permanently correct a customers concern.

Ensure the following conditions are met before programming a control module:

Vehicle system voltage
There is no charging system concern. All charging system concerns must be repaired before programming a control module.
Battery voltage is greater than 12 volts but less than 16 volts. The battery must be charged before programming the control module if the battery voltage is low.
A battery charger is NOT connected to the vehicle's battery. Incorrect system voltage or voltage fluctuations from a battery charger, may cause programming failure or control module damage.
Turn OFF or disable any system that may put a load on the vehicle's battery.
Twilight sentinel
Interior lights
Daytime running lights (DRL)--Applying the parking brake, on most vehicles, disables the DRL system. Refer to the Owners manual.
HVAC systems
Engine cooling fans etc.
The ignition switch is in the proper position. The scan tool prompts you to turn ON the ignition, with the engine OFF. DO NOT change the position of the ignition switch during the programming procedure, unless instructed to do so.
All tool connections are secure.
RS-232
The connection at the data link connector (DLC) is secure.
Voltage supply circuits
DO NOT disturb the tool harnesses while programming. If an interruption occurs during the programming procedure, programming failure or control module damage may occur.
Remote Programming
Turn OFF the ignition.
Install the Tech 2® to the DLC.
Turn ON the ignition, with the engine OFF.
Turn OFF all vehicle accessories.
With the Tech 2®, select Service Programming.
Identify vehicle information as requested by the Tech 2®.
Select the type of module you are programming.
Select the type of programming to be performed.
Verify the displayed VIN with the vehicle VIN. If the displayed VIN does not match the actual VIN, write down the actual VIN and correct the VIN at the Techline® terminal.
When complete, Exit Service Programming.
Turn OFF the Tech 2® and disconnect the Tech 2® from the vehicle.
Turn OFF the ignition.
Connect the Tech 2® to the Techline® terminal.
Select Service Programming.
Select Tech 2® as the tool you are using.
Select the type of programming to be performed.
Verify the displayed VIN with the vehicle VIN. Correct the VIN as necessary.
Select the type of module you are programming.
Identify what type of programming that you are performing.
Normal--This type of programming is for updating an existing calibration or programming a new controller.
Vehicle configuration index (VCI)--This selection is used if the vehicle VIN is unavailable or not recognized by the Techline® terminal. Observe, you will need to contact the Techline® Customer Support center to use this option.
Reconfigure--This is to reconfigure a vehicle, such as tire size and axle ratio changes.
Select the appropriate calibration file.
Ensure all connections are secure.
Select Reprog to initiate the download of the new calibration to the Tech 2®.
After the download is complete, turn OFF the Tech 2®.
Disconnect the Tech 2® from the Techline® terminal.
Install the Tech 2® to the data link connector (DLC).
Turn ON the Tech 2®.
Turn ON the ignition, with the engine OFF.
Select Service Programming.

Important
DO NOT turn OFF the ignition if the programming procedure is interrupted or unsuccessful. Ensure that all the PCM and DLC connections are secure and the Techline® operating software is up to date. Attempt to reprogram the control module. If the control module cannot be programmed, replace the control module. Refer to Powertrain Control Module (PCM) Replacement .

Select Program.
After the download is complete, EXIT Service Programming.
Turn OFF the ignition for 30 seconds.
Turn OFF the Tech 2®.
If a control module is replaced the following service procedures must be performed:
The Crankshaft Variation Learn Procedure
The Engine Oil Life Reset Procedure
The Idle Learn Procedure
The Inspection/Maintenance Complete System Set Procedure
The Vehicle Theft Deterrent Password Learn Procedure
The TP Sensor Learn Procedure
Programming Verification
With a scan tool, clear the DTCs.
Attempt to start the engine.
Repeat the Service Programming procedure if the engine does not start or operates poorly. Perform the following procedures before programming the PCM:
Ensure the control module and DLC connections are OK.
Ensure the Techline® operating software is up to date.
Ensure the calibration part number is correct for the vehicle.
Attempt to program the control module. If the control module still cannot be programmed properly, replace the control module. Refer to Powertrain Control Module (PCM) Replacement . You must program the replacement control module.
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