Data Link Communication System Buick Rendezvous I

Fastener Tightening Specifications

Fastener Tightening Specifications

Data Link Communications Schematic Icons

Data Link Communications Schematic Icons Icon Icon Definition CAUTION: When performing service on or near the SIR components or the SIR wiring, the SIR system must be disabled. Refer to SIR Disabling and Enabling Zones. Failure to observe the correct procedure could cause deployment of the SIR components, personal injury, or unnecessary SIR system repairs

Scheme 1

Scheme 2

Data Link Communications Connector End Views

Data Link Connector (DLC) Connector End Connector Part Information 12110250 16-Way F Metri-Pack 150 Series (BLK) Pin Wire Color Circuit No. Function 1 - - Not Used 2 PPL 1132 DLC Class 2 Serial Data 3 - - Not Used 4 BLK 1450 Ground 5 BLK 1550 Ground 6 TAN/WHT 2500 High Speed GMLAN Serial Data Bus + (LY7) 7-13 - - Not Used 14 TAN 2501 High Speed GMLAN Serial Data Bus - (LY7) 15 - - Not Used 16 ORN 2740 Battery Positive Voltage

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.

Diagnostic Trouble Code (DTC) List

Diagnostic Trouble Code (DTC) List

Circuit Description

Modules connected to the GMLAN High Speed serial data circuit monitor for serial data communications on the GMLAN High Speed network during normal vehicle operation. Operating information and commands are exchanged among the modules. Each module on GMLAN High Speed network maintains a transmit error counter (TEC) and a receive error counter (REC). The counter values increase with detected errors and will decrease with error-free messages. If the TEC value exceeds 255 the controller removes itself from the network and a DTC U0001 will be set.

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 DTC

A certain number of no valid transmitted messages on the GMLAN High Speed serial data circuits are detected by the module.

Action Taken When the DTCs Sets

1. The module suspends all message transmission.
2. The module uses default values for all parameters received on the GMLAN High Speed serial data circuits.
3. The module inhibits the setting of all other GMLAN High Speed communication DTCs.

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

1. This DTC cannot be retrieved with a current status. Diagnosis of current DTC is accomplished via the symptom, Scan Tool Does Not Communicate with High Speed GMLAN High Speed Device. Refer to «Scan Tool Does Not Communicate with High Speed GMLAN Device»(/buick/rendezvous/i-2001-2007/remont/communication-devices/#data-link-communication-system__scan-tool-does-not-communicate-with) .
2. An intermittent condition is likely to be caused by a short on the GMLAN High Speed serial data circuits. Use the Scan Tool Does Not Communicate with High Speed GMLAN Device procedure in order to isolate an intermittent condition. Refer to «Scan Tool Does Not Communicate with High Speed GMLAN Device»(/buick/rendezvous/i-2001-2007/remont/communication-devices/#data-link-communication-system__scan-tool-does-not-communicate-with) .

Modules connected to the GMLAN High Speed serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have prerecorded information about messages exchanged on the serial data circuits. The supervised and periodic messages are used by the receiving module as an availability indicator from the transmitter module. Each message contains the identification number of the transmitting module. When a message indicates availability of the transmitting module is not received, the receiving module sets a DTC Uxxxx. xxxx is equal to the 4-digit transmitter module identification number.

The control module ID number list below provides a method for determining which module is not communicating. A module with a GMLAN High Speed serial data circuits malfunction, or which loses power during the current ignition cycle, will set a Loss of Communication DTC by other modules requiring information from the failed module. The modules able to communicate will set a DTC Uxxxx indicating the module not communicating.

If any of the GMLAN High Speed circuits are shorted to battery voltage, ground or between them, no communication is possible on GMLAN High Speed serial data bus, and a DTC U0073 sets.

GMLAN High Speed ID

1. The ignition is ON and the engine is running.
2. The module supply voltage is in the normal operating range of 9-16 volts.

A receiving module did not detect the GMLAN High Speed serial data supervised periodic message from a transmitting module.

Action Taken When the DTC Sets

1. The module uses a default value for the missing parameter.
2. The malfunction indicator lamp (MIL) will illuminate on the second consecutive ignition cycle that the diagnostic runs and fails, for the type B DTCs.

Conditions for Clearing the MIL/DTC

The MIL or DTC clearing depends on DTC type.

DTC Type B

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

DTC Type C

1. A current DTC and MIL clear 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. A poor connection at the inoperative module may cause this code to set.
2. An improperly powered module may cause this code to set.

Test Description

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

1. 1: A total loss of communication on the GMLAN High Speed serial data link should be diagnosed first.
2. 8: The modules which can communicate indicate the module which cannot communicate. You must clear the DTC from these modules to avoid future misdiagnosis.

DTC U0100-U0299

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 five seconds of beginning serial data communication, DTC U1000 or U1255 is set. When more than one critical parameter does not have an identification number associated with it, 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 and U1301 and U1305 do not have a current status.
3. 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 serial data communication.

The module uses a default value for the missing parameter.

1. A current DTC U1000 or U1255 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 or U1255 will clear upon completion of 100 ignition cycles without a repeated failure.

When a malfunction occurs while modules are communicating, a Lost Communication DTC is set as a current DTC. When the ignition is turned OFF, 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 or U1255 is set current by the other modules. If the malfunction occurs when the modules are not communicating, only DTC U1000 or U1255 is set.

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 or U1255.
2. 2: The modules which are not communicating are the likely cause of U1000 or U1255 being set. The following modules communicate on the class 2 serial data circuit: BCM EBCM ECM HUD HVAC Control Module (CJ2) IPC MSM (A43) PCM Radio SDM TCM Theft Deterrent Control Module VIU (UG1) Devices on the Auxiliary Power Drop Connector
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 which was not communicating may have set Lost Communication with XXX DTCs for those modules that it was monitoring.
6. 11: The modules which can communicate indicate the module which cannot communicate. You must clear the DTC from these modules to avoid future misdiagnosis.
7. 13: If all modules are communicating, the module which set U1000 or U1255 may have done so due to some other condition.
8. 14: The module which set U1000 or U1255 is the likely cause of the malfunction.

DTC U1000 and U1255

DTC U1001 To U1254: Module U1XXX Communication

DTC U1001-U1254

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 tables.
2. The DTC which is reported the most times.
3. From the lowest number DTC to the highest number DTC.

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. 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 is set. The XXX is equal to the 3 digit identification number of the module.

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.

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 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 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.

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

1. 6: 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.

DTC U1001-U1254

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.

DTC U1300, U1301, or U1305

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.

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/rendezvous/i-2001-2007/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/rendezvous/i-2001-2007/remont/communication-devices/#data-link-communication-system) .

Modules connected to the GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. The supervision time-out period is 250 ms. Each message contains the identification number of the transmitter module. When a message that indicates the availability of the transmitter module is not received, the receiver module sets a DTC 21xx where xx is equal to the 2-digit identification number of the transmitter module.

The control module ID number list below provides a method for determining which module is not communicating. A module with a GMLAN 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 module that can communicate will set a DTC indicating the module that can not communicate.

DTC U2105

When more than one Loss of Communication DTC is set in either 1 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. Voltage supplied to the modules is in the normal operating voltage range.
2. The vehicle power mode requires serial data communication to occur.
3. The DTC U2100 does not have a current status.

A supervised periodic message that includes the transmitter module availability has not been received.

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.

1. A poor connection at the inoperative module may cause this code to set.
2. An improperly powered module may cause this code to set.

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

1. 6: The module which was not communicating due to an open in the GMLAN serial data circuits may have set Loss of Communication DTCs for those modules that it was monitoring.
2. 8: The modules which can communicate indicate the module which cannot communicate. You must clear the DTC from these modules to avoid future misdiagnosis.

DTC U2105

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.

Scan Tool Does Not Power Up

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. 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.

1. The BCM detects that the ignition is ON and sends the appropriate power mode message to the other modules. Therefore, the BCM must be connected to the DLC for any other module to communicate with the scan tool.
2. When the class 2 serial data circuit: is shorted to ground is shorted to voltage

The following DTCs may set

1. U1300
2. U1301
3. U1305

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

1. 2: A partial loss of communication in the class 2 serial data circuit uses a different procedure than a total loss of communication of the class 2 serial data circuit.
2. 4: The following DTCs may be retrieved with a history status. These DTCs are not the cause of the present condition. U1300 U1301 U1305
3. 6: 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: Normal class 2 serial data communication cannot take place until the power mode master (PMM) module sends the appropriate power mode message. If the PMM does not send a wake-up message, other modules on the class 2 serial data circuit may not communicate.
5. 12: Normal class 2 serial data communication cannot take place until the power mode master (PMM) module sends the appropriate power mode message. If the PMM does not send a wake-up message, other modules on the class 2 serial data circuit may not communicate.
6. 13: Normal class 2 serial data communication cannot take place until the power mode master (PMM) module sends the appropriate power mode message. If the PMM does not send a wake-up message, other modules on the class 2 serial data circuit may not communicate.
7. 19: If there are no current DTCs that begin with the letter "U", the communication concern has been repaired.
8. 20: The communication concern may have prevented diagnosis of the customer complaint.

Scan Tool Does Not Communicate with Class 2 Device

Scan Tool Does Not Communicate with High Speed GMLAN Device

Modules connected to the GMLAN serial data circuit monitor for serial data communications on the GMLAN network during normal vehicle operation. Operating information and commands are exchanged among the modules.

The engine will not start when there is a total malfunction of the GMLAN serial data circuits while the engine is not running. The following conditions may cause a total loss of GMLAN data communication

1. Any of the GMLAN High Speed serial data circuits shorted to ground.
2. Any of the GMLAN High Speed serial data circuits shorted to voltage.
3. A short between GMLAN High Speed serial data circuits.
4. An internal malfunction of a module on the GMLAN network that causes a short to voltage or ground.

Scan Tool Does Not Communicate with High Speed GMLAN Device

Data Link References

This table identifies which serial data link that a particular module uses for in-vehicle data transmission. Some modules may use more than one data link to communicate. Some modules may have multiple communication circuits passing through them without actively communicating on that data link. This table is used to assist in correcting a communication malfunction. For the description and operation of these serial data communication circuits, refer to Data Link Communications Description and Operation .

Data Link References

Removal Procedure

1. Remove the bolts/screws from the data link connector.
2. Remove the lower data link connector.

Scheme 3

1. Place the data link connector into position. NOTE: Refer to Fastener Notice in Cautions and Notices.
2. Install the bolts/screws to the data link connector. Tighten: Tighten the bolts/screws to 2 N.m (18 lb in).

There are 2 different communication networks on this vehicle: The class 2 network and the GMLAN network. The class 2 serial data link, and the GMLAN High Speed serial data circuit link. Modules that need real time communications are attached to the high speed network. The engine control module (ECM) is the gateway between the networks. The purpose of the gateway is to transfer information from one network to another.

GMLAN Circuit Description

The data link connector (DLC) allows a scan tool to communicate with the GMLAN serial data circuit. On this vehicle, only GMLAN high speed is used. That means that the serial data is transmitted on 2 wires at an average of 500 Kbps. The high speed dual wire GMLAN is a differential bus. That means that two bus lines, GMLAN high and GMLAN low are driven to opposite extremes from a rest or idle level. The idle level which is approximately 2.5 volts is considered a recessive transmitted data and is interpreted as a logic 1. Driving the lines to their extremes means adding 1 volt to GMLAN high wire and subtracting 1 volt from GMLAN low wire. This dominant state is interpreted as a logic 0. GMLAN network management supports selective start up and is based on virtual networks.

A virtual network is a collection of signals started in response to a vehicle event. The starting of a virtual network signifies that a particular aspect of the vehicles functionality has been requested. A virtual network is supported by virtual devices which represents a collection of signals owned by a single physical device. So, any physical device can have one or more virtual devices. The signal supervision is the process of determining whether an expected signal is being received or not. Failsofting is the ability to substitute a signal with a default value or a default algorithm, in the absence of a valid signal. Some messages are also interpreted as a, heartbeat, of a virtual device. If such a signal is lost, the application will set a no communication code against the respective virtual device. This code is mapped on the Tech 2 screen as a code against the physical device. Note that a loss of serial data DTC does not normally represent a failure of the module that set it.

Class 2 Circuit Description

The data link connector (DLC) allows a scan tool to communicate with the class 2 serial data line. The serial data line is the means by which the microprocessor-controlled modules that are connected to it communicate with each other. Once the scan tool is connected to the class 2 serial data line through the DLC, the scan tool can be used to monitor each module for diagnostic purposes and to check for diagnostic trouble codes (DTCs). Class 2 serial data is transmitted on a single wire at an average of 10.4 Kbps. The bus is active at 7.0 volts nominal and inactive at ground potential. When the ignition switch is in RUN, each module communicating on the class 2 serial data line sends a state of health (SOH) message every 2 seconds to ensure that the module is operating properly.

When a module stops communicating on the class 2 serial data line, for example if the module loses power or ground, the SOH message it normally sends on the data line every 2 seconds disappears. Other modules on the class 2 serial data line, which expect to receive that SOH message, detect its absence; those modules in turn set an internal DTC associated with the loss of SOH of the non-communicating module. The DTC is unique to the module which is not communicating, for example, when the body control module (BCM) SOH message disappears, several modules set DTC U1064. Note that a loss of serial data DTC does not normally represent a failure of the module that set it.

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 signal at terminal 2
5. GMLAN High Speed + circuit at terminal 6
6. GMLAN High Speed - circuit at terminal 14

GMLAN Serial Data Line

The GMLAN serial data communications circuit used on this vehicle is in a linear topology. The following modules are connected to the link, in order from DLC to the end of the linear configuration

The following modules communicate on the GMLAN serial data circuit

1. The engine control module (ECM) - 3.6L
2. The transmission control module (TCM) - 3.6L

Class 2 Serial Data Link

The class 2 serial data link allows these modules to communicate data with each other

1. Body Control Module (BCM)
2. Electronic Brake Control Module (EBCM)
3. Heads Up Display (HUD)
4. HVAC Control Module (with CJ2)
5. Inflatable Restraint Sensing Diagnostic Module (SDM)
6. Instrument Panel Cluster (IPC)
7. Memory Seat Module (MSM) (with A43)
8. Powertrain Control Module (PCM) - 3.4L
9. Radio
10. Rear Seat Entertainment (RSE)
11. Theft Deterrent Control Module
12. Vehicle Communication Interface Module (VCIM)
13. Devices on the auxiliary power drop connector

In addition, the class 2 serial data link allows a scan tool to communicate with these modules for diagnostic and testing purposes.

See also:
• Control Module References
• Circuit Testing
• Wiring Repairs
• Testing for Intermittent Conditions and Poor Connections
• Connector Repairs
• Master Electrical Component List
• Inline Harness Connector End Views
• Body Control System Description and Operation
• DTC U0001
• DTC U1001-U1254
• Scan Tool Does Not Communicate with High Speed GMLAN Device
• Data Link Communications Connector End Views