Sierra Denali RWD V8-6.2L (2009)
issue.
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Communication may be available between the BCM and the scan tool with the high speed GMLAN serial data system inoperative. This condition
is due to the BCM using both the high and low speed GMLAN systems.
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An open in the DLC ground circuit terminal 5 will allow the scan tool to operate but not communicate with the vehicle. When the scan tool
attempts to communicate with the vehicle a message "no CANdi module detected" will be displayed.
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The engine will not start when there is a total malfunction of the high speed GMLAN serial data bus.
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Technicians may find various Local Area Network (LAN) communication Diagnostic Trouble Codes (DTC) and no low speed GMLAN
communications with the scan tool.
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The engine will not start when there is a total malfunction of the high speed GMLAN serial data bus.
These conditions may be caused by the installation of an aftermarket navigation radio module (see bulletins). Some customers may comment of
one or more of the following concerns:
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Vehicle will not crank.
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Vehicle cranks but will not start.
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Vehicle stability enhancement system warning lights and messages.
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PRNDL gear indicator position errors.
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Tire Pressure Monitor (TPM) system warning lights.
Reference Information
Schematic Reference
Data Communication Schematics (See: Diagrams/Electrical Diagrams)
Connector End View Reference
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Component Connector End Views (See: Diagrams/Connector Views)
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Splice Pack Connector End Views (See: Diagrams/Connector Views)
Description and Operation
Data Link Communications Description and Operation (See: Description and Operation)
Electrical Information Reference
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Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics)
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Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics)
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Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics)
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Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics)
Circuit/System Testing
Note
Use the schematic to identify the following:
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Control modules the vehicle is equipped with
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Control module locations on the low speed GMLAN serial data circuit
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Each control module's low speed GMLAN serial data circuit terminals
1. Attempt to communicate with all control modules on the low speed GMLAN serial data circuit, refer toData Link References (See: Initial
Inspection and Diagnostic Overview/Data Link References) . Communications should not be available with two or more control modules on the
low speed GMLAN serial data circuit.
‹› If only one control module is not communicating, diagnose that control module only, refer toDTC U0100-U0299 (See: Testing and
Inspection/Diagnostic Trouble Code Tests and Associated Procedures/U Code Charts/U0100) .
‹› If one or more control modules are communicating but not all, refer to Testing the Serial Data Circuit for an Open/High Resistance.
2. Disconnect the scan tool from the DLC. The following tests will be done at the DLC connector.
3. All access doors closed, ignition OFF for 60 seconds, test for less than 10 ohm between the ground circuit terminal 5 and ground.
‹› If greater than the specified range, test the ground circuit for an open/high resistance.
4. Ignition ON, test for less than 4.5 V between the serial data circuit terminal 1 and ground.
‹› If greater than the specified range, test the serial data circuit for a short to voltage, refer to Testing the Serial Data Circuit for a Short to
Voltage.
5. Ignition OFF for 60 seconds, test for greater than 100 ohm between the serial data circuit terminal 1 and ground.
