Data Link Communication System Buick LeSabre VIII

Scheme 45

Data Link Connector (DLC) Schematics

See COMPUTER DATA LINES .

Scheme 46

Scheme 47

Diagnostic Starting Point - Data Link Communications

Begin the diagnosis of the data link communications by performing the Diagnostic System Check for the system in which the customer concern is apparent. The Diagnostic System Check will direct you to the correct procedure within the Data Link Communications section when a communication malfunction is present.

Scheme 48

Circuit Description

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the identification number of the module which sent the message for State of Health monitoring Node Alive messages. A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. When a module does not associate an identification number with at least one critical parameter within 5 seconds of beginning serial data communication, DTC U1000 or DTC U1255 is set. When more than one critical parameter has the same module identification number associated with it, the DTC will only be reported once. Modules communicating on the class 2 serial data circuit can include the following

1. Dash Integration Module (DIM)
2. Driver Door Module (DDM)
3. Electronic Brake Control Module (EBCM)
4. Head Up Display (HUD) w/UV6
5. HVAC Control Module w/C67
6. Inflatable Restraint Sensing and Diagnostic Module (SDM)
7. Instrument Panel Cluster (IPC)
8. Instrument Panel Integration Module (IPM) w/CJ2
9. Memory Seat Module (MSM) w/A45
10. Powertrain Control Module (PCM)
11. Radio
12. Rear Integration Module (RIM)
13. Remote Control Door Lock Receiver (RCDLR)
14. Remote Playback Device - CD Changer w/U1S
15. Theft Deterrent Control Module
16. Vehicle Communication Interface Module (VCIM) Generation-F1
17. Vehicle Interface Unit (VIU) Generation-2.6

Conditions for Running the DTC

1. The following DTCs do not have a current status: B1327 B1328 U1300 U1301 U1305
2. The vehicle power mode requires serial data communication to occur.

Conditions for Setting the DTC

At least one critical operating parameter has not been associated with an identification number within about 5 seconds after beginning class 2 serial data communication.

Action Taken When the DTC Sets

The module uses a default value for the missing parameter.

Conditions for Clearing the DTC

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Diagnostic Aids

When a malfunction such as an open fuse to a module occurs while modules are communicating, a DTC U1001-1254 Loss of XXX Communications is set current. When the modules stop communicating the current DTC U1001-1254 Loss of XXX Communications is cleared but the history DTC remains. When the modules begin to communicate again, the module with the blown fuse will not be learned by the other modules so U1000 or U1255 is set current by the other modules. If the malfunction occurs when the modules are not communicating, only U1000 or U1255 is set.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 1. A DTC U1001 - U1254 "Lost Communications with XXX" with a history status may indicate the cause of U1000 or U1255.
2. 2. The modules not communicating are the likely cause of U1000 or U1255. The modules that are available on the class 2 serial data circuit are listed in the Circuit Description.
3. 7. The module which was not communicating due to a poor connection to the class 2 serial data circuit may have set DTC U1001 - U1254 "Lost Communications with XXX" for those modules that it was monitoring.
4. 9. The modules which can communicate indicate the module which cannot communicate. You must clear the serial data communication DTCs from these modules to avoid future misdiagnosis.
5. 12. If all modules are communicating, the module which set U1000 or U1255 may have done so due to some other condition.
6. 14. The module which set U1000 or U1255 is the likely cause of the malfunction.

Scheme 49

Scheme 50

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the identification number of the module which sent the message for State of Health monitoring Node Alive messages. A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. Once an identification number is learned by a module, it will monitor for that module's Node Alive message. Each module on the class 2 serial data circuit which is powered and performing functions that require detection of a communications malfunction is required to send a Node Alive message every 2 seconds. When no message is detected from a learned identification number for 5 seconds, a DTC U1XXX where XXX is equal to the three digit identification number is set.

The control module ID number list below provides a method for determining which module is not communicating. A module with a class 2 serial data circuit malfunction or which loses power during the current ignition cycle will have a Loss of Communication DTC set by other modules that depend on information from that failed module. The modules that can communicate will set a DTC indicating the module that can not communicate. When no message is detected from a learned identification number for 5 seconds, a DTC U1XXX where XXX is equal to the 3 digit identification number is set.

Scheme 51

Scheme 52

When more than one Loss of Communication DTC is set in either one module or in several modules, diagnose the DTCs in the following order

1. Current DTCs before history DTCs unless told otherwise in the diagnostic table.
2. The DTC which is reported the most times.
3. From the lowest number DTC to the highest number DTC.

1. The following DTCs do not have a current status: B1327 B1328 U1300 U1301 U1305
2. The vehicle power mode requires serial data communication to occur.

At least one critical operating parameter has not been associated with an identification number within about 5 seconds after beginning class 2 serial data communication.

The module uses a default value for the missing parameter.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

When multiple Loss of Communication DTCs are set concurrently, the cause is likely to be 2 opens in the ring portion of the class 2 serial data circuit. Use the Control Module ID Number list in order to determine which modules are not communicating. Use the class 2 serial data circuit schematic in order to determine the location of the opens.

The number below refers to the step number on the diagnostic table.

1. 8. The module which was not communicating on the class 2 serial data circuit may have set Loss of Communication DTCs for those modules that it was monitoring.

Scheme 53

Scheme 54

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. In addition to this, Node Alive messages are transmitted by each module on the class 2 serial data circuit about once every 2 seconds. When the module detects one of the following conditions on the class 2 serial data circuit for approximately 3 seconds, the setting of all other class 2 serial communication DTCs is inhibited and a DTC will set.

Scheme 55

Conditions for Running the DTCs

1. Voltage supplied to the module is in the normal operating voltage range.
2. The vehicle power mode requires serial data communication to occur.

Conditions for Setting the DTCs

1. No valid messages are detected on the class 2 serial data circuit.
2. The voltage level detected on the class 2 serial data circuit is under one of the following conditions: High Low
3. The above conditions are met for approximately 3 seconds.

Action Taken When the DTCs Sets

The module uses default values for all parameters received on the class 2 serial data circuit.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. These DTCs cannot be retrieved with a current status. Diagnosis of current DTCs is accomplished via the symptom, Scan Tool Does Not Communicate with a Class 2 Device. Refer to «Scan Tool Does Not Communicate with Class 2 Device»(/buick/lesabre/viii-2000-2005/remont/communication-devices/#data-link-communication-system) .
2. An intermittent condition is likely to be caused by a short on the class 2 serial data circuit. Use the Scan Tool Does Not Communicate with a Class 2 Device procedure in order to isolate an intermittent condition. Refer to «Scan Tool Does Not Communicate with Class 2 Device»(/buick/lesabre/viii-2000-2005/remont/communication-devices/#data-link-communication-system) .

Symptoms - Data Link Communications

Note. The following steps must be completed before using the symptom tables. Perform the applicable diagnostic system check before using the Symptom Tables in order to verify that there are no DTCs set. Review the system operation in order to familiarize yourself with the system functions. Refer to Data Link Communications Description and Operation .

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the vehicle systems.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS .

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «Scan Tool Does Not Power Up»(/buick/lesabre/viii-2000-2005/remont/communication-devices/#data-link-communication-system)
2. «Scan Tool Does Not Communicate with Class 2 Device»(/buick/lesabre/viii-2000-2005/remont/communication-devices/#data-link-communication-system)

The Data Link Connector (DLC) is a standardized 16 cavity connector. Connector design and location is dictated by an industry wide standard, and is required to provide the following

1. Scan tool power battery positive voltage at terminal 16
2. Scan tool power ground at terminal 4
3. Common signal ground at terminal 5

The scan tool will power up with the ignition OFF. Some modules however, will not communicate unless the ignition is ON and the Power Mode Master (PMM) module sends the appropriate power mode message.

The number below refers to the step number on the diagnostic table.

1. 4. If the battery positive voltage and ground circuits of the DLC are functioning properly. The malfunction must be due to the scan tool.

Scheme 56

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. Connecting a scan tool to the DLC allows communication with the modules for diagnostic purposes.

The engine will not start when there is a total malfunction of the class 2 serial data circuit while the engine is not running. The following conditions will cause a total loss of class 2 serial data communication

1. A class 2 serial data circuit shorted to ground.
2. A class 2 serial data circuit shorted to voltage.
3. An internal malfunction of a module on the class 2 serial data circuit that causes a short to voltage or ground.

The numbers below refer to the step numbers on the diagnostic table.

1. 2. A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit.
2. 3. The following DTCs may be retrieved with a history status. These DTCs are not the cause of the present condition. U1300 U1301 U1305
3. 8. A State of Health DTC with a history status may be present along with a U1000 or U1255 with a current status. This indicates that the malfunction occurred when the ignition was on.
4. 10. Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
5. 12. An open between the DLC and the class 2 serial data circuit will prevent the scan tool from communicating with any module. This condition will not set a DTC.
6. 13. Splitting the class 2 serial data circuit will help isolate the location of the malfunction. If communication can be established, the malfunction is located in the wiring or one of the modules that is no longer connected to the DLC. If communication cannot be established, the malfunction is located in the wiring or one of the modules that is still connected to the DLC.
7. 21. If there are no current DTCs that begin with the letter "U" the communication malfunction has been repaired.
8. 22. The communication malfunction may have prevented diagnosis of the customer complaint.

Scheme 57

Scheme 58

Scheme 59

Scheme 60

Data Link Connector (DLC)

The Data Link Connector (DLC) is a standardized 16 cavity connector. Connector design and location is dictated by an industry wide standard, and is required to provide the following

1. Scan tool power battery positive voltage at terminal 16.
2. Scan tool power ground at terminal 4.
3. Common signal ground at terminal 5.
4. Class 2 serial data at terminal 2.

The scan tool will power up with the ignition off. Some modules however, will not communicate unless the ignition is on and the Power Mode Master (PMM) module sends the appropriate power mode message.

Class 2 Serial Data Link

The data link is configured as a ring with discrete lines entering and leaving each module. This allows communications to the modules on the ring if one of the two discrete circuits is open.

A total list of the control modules on the Class 2 Serial Data Line can include the following

1. Dash Integration Module (DIM)
2. Driver Door Module (DDM)
3. Electronic Brake Control Module (EBCM)
4. Head Up Display (HUD) w/UV6
5. HVAC Control Module w/C67
6. Inflatable Restraint Sensing and Diagnostic Module (SDM)
7. Instrument Panel Cluster (IPC)
8. Instrument Panel Integration Module (IPM) w/CJ2
9. Memory Seat Module (MSM) w/A45
10. Powertrain Control Module (PCM)
11. Radio
12. Rear Integration Module (RIM)
13. Remote Control Door Lock Receiver (RCDLR)
14. Remote Playback Device - CD Changer w/U1S
15. Theft Deterrent Control Module
16. Vehicle Communication Interface Module (VCIM) Generation-F1
17. Vehicle Interface Unit (VIU) Generation-2.6

The following modules have only one communication line connection to the Class 2 data circuit

1. Driver Door Module (DDM)
2. Head Up Display (HUD) w/UV6
3. Memory Seat Module (MSM) w/A45
4. Vehicle Communication Interface Module (VCIM) Generation-F1
5. Vehicle Interface Unit (VIU) Generation-2.6

Power Door Serial Data Line

The Power Door Serial Data Line does not communicate with the scan tool via the DLC. Power door serial data information is interpreted by the Driver Door Module (DDM) and transmitted on the Class 2 data line by the DDM.

The power door serial data is used for serial data communication between the door modules as well as the Driver Door Window Switch Assembly (DDSA).

See also:
• TESTING FOR INTERMITTENT AND POOR CONNECTIONS
• Scan Tool Does Not Communicate with Class 2 Device