Cobalt L4-2.2L (2008)
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If there are multiple modules, test each serial data circuit for a short to voltage or a short to ground, with the modules disconnected. If the
circuit tests normal, install each module one at a time starting with the closest module to the splice pack until communications stop. Replace
the faulty module.
8. If all circuits test normal, test or replace the splice pack.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair. See: Testing and Inspection/Diagnostic Trouble Code Tests and Associated
Procedures/Verification Tests and Procedures
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GMLAN Wiring Repairs
Scan Tool Does Not Power Up
Scan Tool Does Not Power Up
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.
Circuit/System Description
The data link connector (DLC) is a standardized 16-cavity connector. Design and location is dictated by an industry-wide standard. The following is
required to be provided:
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Scan tool power battery positive voltage at terminal 16
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Scan tool power ground at terminal 4
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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.
Circuit/System Verification
1. Ignition OFF, test for less than 5 ohm between terminal 4 at the data link connector (DLC) and ground.
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If greater than the specified value, test the ground circuit for an open/high resistance.
2. Ignition OFF, test for less than 5 ohm between the DLC terminal 5 and ground.
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If greater than the specified value, test the ground circuit for an open/high resistance.
3. Ignition ON, test for B+ between the DLC terminals 16 and ground.
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If not the specified value, test the B+ circuit for a short to ground or an open/high resistance.
4. If all circuits test normal, refer to the scan tool user guide.
