Outlook AWD V6-3.6L (2008)
Scan Tool Does Not Communicate with Low Speed GMLAN Device
Diagnostic Instructions
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Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Testing and Inspection/Initial Inspection and
Diagnostic Overview/Diagnostic System Check - Vehicle
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Review Strategy Based Diagnosis for an overview of the diagnostic approach.
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Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
Modules connected to the low speed GMLAN serial data circuit 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 low speed GMLAN serial
data circuit uses JX 205 and JX 405 as common connection points between some modules and the data link connector (DLC).
Diagnostic Aids
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Use the Data Link References to identify the low speed GMLAN serial data modules.
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This test is used for a total low speed GMLAN communication failure. 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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An open in the low speed GMLAN serial data circuit between the splice pack and a module will only effect the specific module. This type of
failure will set a loss of communication DTC for each module effected, and the other modules will still communicate.
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An open in the 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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An open between the DLC and JX 205 will only effect the communication with the scan tool. The vehicle modules will still communicate, and the
vehicle will start.
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The engine will not start when there is a total malfunction of the low speed GMLAN serial data circuit.
The following conditions may cause a total loss of low speed GMLAN data communication:
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The low speed GMLAN serial data circuit shorted to ground or voltage.
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A module internal malfunction that causes a short to voltage or ground on the low speed GMLAN circuit.
Circuit/System Testing
1. Test for less than 1.0 ohm between the ground circuit terminal 5 of the DLC and ground.
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If greater than the specified range, test the ground circuit for open/high resistance.
2. Ignition OFF, disconnect the harness connector at JX 205.
3. Ignition ON, test for less than 1 volt between the serial data circuit terminal 1 of the DLC and ground.
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If greater than the specified range, test the serial data circuit for a short to voltage.
4. Test for infinite resistance between the serial data circuit terminal 1 of the DLC and ground.
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If less than the specified value, test the serial data circuit for a short to ground.
5. Test for less than 2 ohms on the serial data circuit between terminal 1 of the DLC and terminal 1 of JX 205.
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If greater that the specified range, test the serial data circuit for an open/high resistance.
