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Contents Wiring diagrams Section: Communication Devices All sections

Data Link Communications System Buick Century VI

Communication Devices 18 illustrations ~2538 words

Specifications

ApplicationSpecification
MetricEnglish
Data Link Connector Screw2 N.m18 lb in

Fastener Tightening Specifications

Scheme 1

Scheme 1: Schematic and Routing Diagrams
Scheme 1: Schematic and Routing Diagrams

Scheme 2

Scheme 2
Scheme 2

Scheme 3

Scheme 3: Data Link Communications Component Views
Scheme 3: Data Link Communications Component Views

Scheme 4

Scheme 4: Data Link Communications Connector End Views
Scheme 4: Data Link Communications Connector End Views

Scheme 5

Scheme 5
Scheme 5

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 6

Scheme 6: Diagnostic Starting Point - Data Link Communications
Scheme 6: Diagnostic Starting Point - Data Link Communications

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. 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 about 5 seconds of beginning serial data communication, DTC U1000 or U1255 is set. If more than one critical parameter does not have an identification number association, the DTC will only be reported once.

Conditions for Running the DTC

  1. Voltage supplied to the module is in the normal operating voltage range of 9-16 volts.
  2. Diagnostic trouble codes U1300, U1301 and U1305 do not have a current status.
  3. The module operation or 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 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 U1000 will clear when all critical operating parameters for the module have been associated with an identification number, or at the end of the current ignition cycle.
  2. A history DTC U1000 will clear after 50 ignition switch ON/OFF cycles with no repeat of the failure.

Diagnostic Aids

When a malfunction, such as an open fuse to a module occurs while modules are communicating, a Lost Communication DTC for a specific module is set as a current DTC. When the modules stop communicating the current Lost Communication DTC is cleared, but the history DTC remains. When the modules begin to communicate again, the module with the open fuse will not be learned by the other modules, so DTC U1000 is set current by the other modules. If the malfunction occurs when the modules are not communicating, only DTC U1000 or U1255 is set.

Test Description

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

  1. 1. A Lost Communication with XXX DTC with a history status may indicate the cause of U1000.
  2. 2. The modules that is not communicating is the likely cause of U1000 or U1255 being set. The following modules communicate on the class 2 serial data circuit: PCM EBCM SDM IPC BCM HVAC Control Module VCIM
  3. 5. The module which was not communicating may have set Lost Communication with XXX DTCs for those modules that it was monitoring.
  4. 6. The module which was not communicating may have set Lost Communication with XXX DTCs for those modules that it was monitoring.
  5. 7. The module that was not communicating may have set Lost Communication with XXX DTCs for those modules that the module was monitoring.
  6. 11. The modules that communicate indicate the module that cannot communicate. You must clear the DTC from the modules in order to avoid future misdiagnosis.
  7. 13. If all modules are communicating, the module that set U1000 may have done so due to some other condition.
  8. 14. The module that set U1000 is the likely cause of the malfunction.

Scheme 7

Scheme 7
Scheme 7

Scheme 8

Scheme 8
Scheme 8

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, the module will monitor for the sending module's Node Alive message. Each module on the class 2 serial data circuit which is performing functions that require detection of a communication 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 3 digit identification number is set.

The Control Module ID Number list provides a method for determining which module is not communicating. A module with an internal class 2 serial data circuit malfunction or which loses power during the current ignition cycle would have a Lost Communication DTC set by other modules. The modules that can communicate will set a DTC indicating the module that cannot communicate. When no message is detected from a learned identification number for 5 seconds, a DTC U1xxx is set.

Scheme 9

Scheme 9: Circuit Description
Scheme 9: Circuit Description

When more than 1 Loss of Communication DTC is set in either one module or several modules, diagnose the DTCs in the following order

  1. Current DTCs before history DTCs, unless told otherwise in the diagnostic tables
  2. The DTC which is reported the most times
  3. From the lowest number DTC to the highest number DTC.
  1. Voltage supplied to the module is in the normal operating voltage range of 9 to 16 volts
  2. Diagnostic trouble codes U1300 and U1301 do not have a current status
  3. The module operation or vehicle power mode requires serial data communication to occur.

A message from a learned identification number has not been detected for the past 5 seconds.

  1. A current DTC will clear when a Node Alive message from the failed identification number is detected on the class 2 serial data circuit or at the end of the current ignition cycle
  2. A history DTC will clear after 50 ignition switch ON/OFF cycles with no repeated failure.

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

  1. 1. A module which loses power supply during an ignition cycle will cause other modules to set Lost Communication DTCs.
  2. 2. A module which loses ground during an ignition cycle will cause other modules to set Lost Communication DTCs.
  3. 3. The malfunction is due to an open in the class 2 serial data circuit or an open in the module.
  4. 7. The module which was not communicating may have set Lost Communication DTCs for those modules that it was monitoring.
  5. 9. The modules which can communicate indicate the module which cannot communicate. You must clear the DTC from these modules in order to avoid future misdiagnosis.

Scheme 10

Scheme 10
Scheme 10

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 11

Scheme 11: Circuit Description
Scheme 11: Circuit Description

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 in 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/century/vi-1997-2005/remont/communication-devices/#data-link-communications-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/century/vi-1997-2005/remont/communication-devices/#data-link-communications-system) .

Symptoms - Data Link Communications

IMPORTANTThe following steps must be completed before using the symptom tables
  1. Perform the Diagnostic System Check for the subsystem exhibiting the symptoms. Refer to «CONTROL MODULE REFERENCES»(/buick/century/vi-1997-2005/remont/communication-devices/#body-control-system) in Body Control System. The subsystem diagnostic system check will identify where to begin diagnosis of the data link communication system.
  2. Review the system operation in order to familiarize yourself with the system functions. Refer to «DATA LINK COMMUNICATIONS DESCRIPTION AND OPERATION»(/buick/century/vi-1997-2005/remont/communication-devices/#data-link-communications-system) .

Visual/Physical Inspection

  1. Inspect for aftermarket devices that could affect the operation of the serial data communications systems. Refer to «CHECKING AFTERMARKET ACCESSORIES»(/buick/century/vi-1997-2005/remont/body-electrical/#wiring-systems__checking-aftermarket-accessories) in Wiring Systems.
  2. Inspect the easily accessible systems or visible system components for obvious damage or conditions that 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 in Wiring Systems.

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/century/vi-1997-2005/remont/communication-devices/#data-link-communications-system)
  2. «SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE»(/buick/century/vi-1997-2005/remont/communication-devices/#data-link-communications-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 12

Scheme 12
Scheme 12

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.

Diagnostic trouble codes (DTCs) may be set due to this symptom and during this diagnostic procedure. Complete the diagnostic procedure in order to ensure all the DTCs are diagnosed and cleared from memory.

The BCM detects the ignition switch position and sends the appropriate power mode message to the other modules. The BCM must be connected to the class 2 serial data circuit for any other module to communicate with the scan tool.

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. The following modules communicate on the class 2 serial data circuit: PCM EBCM SDM IPC BCM HVAC Control Module VCIM.
  2. 3. The following DTCs may be retrieved with a history status, but are not the cause of the present condition. U1300 U1301
  3. 6. A State of Health DTC for a specific module 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. 7. Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.
  5. 9. A poor connection at the star connector terminal for the DLC would cause this condition but will not set a DTC.
  6. 10. An open in the class 2 serial data circuit between the DLC and star connector will prevent the scan tool from communicating with any module. This condition will not set a DTC.
  7. 11. The BCM detects the ignition switch position and sends the appropriate power mode message to the other modules. The BCM must remain connected to the DLC for any other module to communicate with the scan tool. This test isolates the BCM class 2 serial data circuit.
  8. 13. This test isolates the PCM class 2 serial data circuit.
  9. 15. This test isolates the EBCM class 2 serial data circuit.
  10. 17. This test isolates the SDM class 2 serial data circuit.
  11. 19. This test isolates the IPC class 2 serial data circuit.
  12. 21. This test isolates the HVAC Control Module class 2 serial data circuit.
  13. 23. This test isolates the VCIM class 2 serial data circuit.
  14. 26. The communication malfunction may have prevented diagnosis of the customer complaint.
  15. 27. If there are no current DTCs that begin with a "U", the communication malfunction has been repaired.

Scheme 13

Scheme 13
Scheme 13

Scheme 14

Scheme 14
Scheme 14

Scheme 15

Scheme 15
Scheme 15

Scheme 16

Scheme 16
Scheme 16

Scheme 17

Scheme 17: Removal Procedure
Scheme 17: Removal Procedure
  1. Remove the screws from the data link connector.
  2. Reposition the data link connector from the instrument panel.

Installation Procedure

Note. Refer to FASTENER NOTICE in Cautions and Notices.

Scheme 18

Scheme 18: Installation Procedure
Scheme 18: Installation Procedure
  1. Position the data link connector to the instrument panel.
  2. Install the screws to the data link connector. Tighten Tighten the screws to 2 N.m (18 lb in).

Data Link Connector (DLC)

The DLC is a standardized 16 way connector located below the instrument panel and close to the steering column. Both the connector design and location are dictated by industry wide agreement to follow SAE J1962 standards.

All data link connectors are required to provide a power supply, hot at all times, to Pin 16. This circuit is used to power the scan tool. All data link connectors provide a power ground at Pin 4 and a clean signal ground at Pin 5.

Class 2 Serial Data Link

The class 2 serial data communications circuit is provided at Pin 2 of the DLC.

The class 2 serial data link allows the following modules to communicate and share data with each other

  1. Body Control Module (BCM)
  2. Electronic Brake Control Module (EBCM)
  3. HVAC Control Module (w/CJ2)
  4. Inflatable Restraint Sensing and Diagnostic Module (SDM)
  5. Instrument Panel Cluster (IPC)
  6. Powertrain Control Module (PCM)
  7. Vehicle Communications Interface Module (VCIM), if equipped

The class 2 serial data link allows a scan tool to communicate with the above modules for diagnostic and testing purposes.

E and C Serial Data Link

The E and C serial data communications circuit is provided at Pin 14 of the DLC.

The E and C serial data link allows the following modules to communicate and share data with each other

  1. Radio
  2. Vehicle Communications Interface Module (VCIM), if equipped

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