H3 V8-5.3L (2008)
Circuit Description
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 data link connector (DLC) allows communication with the modules for
diagnostic purposes. DTCs may be set due to this symptom and during this diagnostic procedure.
Diagnostic Aids
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This test is used for a total class 2 communication failure. If only 1 module is not communicating and sets no DTC, ensure that the vehicle is
equipped with the module, then use DTC U1001-U1254 (See: Testing and Inspection/Diagnostic Trouble Code Tests and Associated
Procedures/U Code Charts/U1016) for diagnostics.
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An open in the class 2 serial data circuit between the DLC and the BCM will only effect the scan tool communication and will not effect module to
module communication
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An open between the data link connector (DLC) and The BCM 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 may not start when there is a total malfunction of the class 2 serial data circuit.
The following conditions may cause a total loss of low speed GMLAN data communication:
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The class 2 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 class 2 serial data circuit.
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When the class 2 serial data circuit is shorted to ground or to voltage, the following DTCs may set as history. If the short is removed and
communication returns, these DTCs indicate an intermittent condition.
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U1300
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U1301
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U1305
Reference Information
Schematic Reference
Data Communication Schematics (See: Diagrams/Electrical Diagrams)
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views/Component Connector End Views)
Description and Operation
Data Link Communications Description and Operation (See: Description and Operation)
Electrical Information Reference
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Circuit Testing (See: Diagrams/Diagnostic Aids/General Electrical Diagnostic Procedures/Circuit Testing/Circuit Testing)
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Connector Repairs (See: Diagrams/Diagnostic Aids/General Electrical Diagnostic Procedures/Connector Repairs/Connector Repairs)
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Testing for Intermittent Conditions and Poor Connections (See: Diagrams/Diagnostic Aids/General Electrical Diagnostic Procedures/Circuit
Testing/Testing For Intermittent and Poor Connections)
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Wiring Repairs (See: Diagrams/Diagnostic Aids/General Electrical Diagnostic Procedures/Wiring Repairs/Wiring Repairs)
Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning) for scan tool information
Circuit/System Testing
1. Test for less than 1.0 ohm of resistance between the DLC ground circuit terminal 5 and ground.
‹› If greater than 1.0 ohm, test the ground circuit for open/high resistance.
Important: Cycle the ignition Key OFF before each module disconnect and ON to attempt communication.
