VUE FWD V6-3.5L (2008)
Circuit/System Description
Modules connected to the high speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating
information and commands are exchanged among the modules when the ignition switch is in any position other than OFF. The high speed GMLAN serial
data circuits must be operational for the vehicle to start due to body control module (BCM) and engine control module (ECM) communications. The
vehicle theft deterrent (VTD) module and ECM exchange information using the BCM as the gateway module allowing communication between the high
and low speed serial data buses. The low speed GMLAN serial data circuit must also be operational for vehicle starting. The high speed GMLAN serial
data bus uses two 120-ohm terminating resistors that are in parallel with the high speed GMLAN (+) and (-) circuits. One of the resistors is in the rear
cargo area and the other is internal to the ECM.
Diagnostic Aids
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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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Use the Date Link References (See: Initial Inspection and Diagnostic Overview/Data Link References) to identify the high speed GMLAN serial
data modules.
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This test is used for a total high speed GMLAN communication malfunction. If only one module is not communicating and sets no DTC, ensure
that the vehicle is equipped with the module, then use DTC U0100-U0299 for diagnostics.
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Some modules may not have internal protection for specific voltage outputs and may open a battery positive voltage or ignition voltage source
fuse. If a voltage input fuse is open and no short is found in that circuit, ensure that no module output voltage circuit is shorted to ground before
replacing the module.
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An open in the data link connector (DLC) ground circuit terminal 5 will allow the scan tool to operate to set up the vehicle on the tool and then not
communicate with the vehicle. When the scan tool is to the point of communicating with the vehicle, a message on the scan tool will indicate "no
CANdi module detected" and will not communicate.
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The engine will not start when there is a total malfunction of the high speed GMLAN serial data bus. The following conditions may cause a total
loss of high speed GMLAN data communication:
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A short between high speed GMLAN (+) and high speed GMLAN (-) circuits
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Any of the high speed GMLAN serial data circuits shorted to ground or voltage
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A module internal malfunction that causes a short to voltage or ground on the high speed GMLAN circuits
Reference Information
Schematic Reference
Data Communication Schematics (See: Diagrams/Electrical Diagrams)
Connector End View Reference
Component 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)
Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning) for scan tool information
Circuit/System Verification
