Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 928 (DATA COMMUNICATION SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESSCAN TOOL DOES NOT COMMUNICATE WITH LOW SPEED GMLAN DEVICECIRCUIT/SYSTEM TESTING
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6
Circuit/System Testing
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Circuit/System Testing
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2007 GMC Yukon XL, 2007 GMC Yukon, 2007 Chevrolet Tahoe, 2007 Chevrolet Suburban, and 2007 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
- Test for less than 1 ohm of resistance between the DLC ground circuit terminal 5 and ground.
- If greater than 1 ohm, test the ground circuit for open/high resistance.
- Ignition OFF, disconnect the harness connector at splice pack SP 300.
- Ignition ON, with a scan tool, attempt to communicate with the instrument panel cluster (IPC). Communication should be available.
- If no communication, disconnect the modules still connected to the DLC one at a time, starting with the furthest from the DLC and attempt to communicate after each disconnect. When communication occurs, test the serial data circuit for a short to ground and a short to voltage between the last module disconnected and the previous module disconnected. If the circuit tests normal, replace the last module disconnected. If no communication is possible, test the serial data circuit for a short to ground, a short to voltage or an open/high resistance between the last module disconnected and the DLC. If the circuit tests normal, replace the last module disconnected.
- Install a 3-amp fused jumper wire between pin A and pin M of the splice pack. Install another 3-amp fused jumper wire to pin L.
- Using the open end of the jumper wire at pin L, connect to splice pack terminals B through K and attempt to establish communications with each module connected to the splice pack, one at a time. Each module should be able to communicate.
- If communications cannot be established with any module after connecting an individual module, replace the module that caused the no communication.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.