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 G3500, VAN CARGO EXTENDED, 4.8 CREPAIR AND DIAGNOSISACCESSORIES & EQUIPMENTCOMMUNICATION DEVICESDATA COMMUNICATION SYSTEMDIAGNOSTIC INFORMATION AND PROCEDURESSCAN TOOL DOES NOT COMMUNICATE WITH LOW SPEED GMLAN DEVICECIRCUIT/SYSTEM TESTING
2008 Chevrolet Chevy Express G3500, Van Cargo Extended, 4.8 C
Circuit/System Testing
2008 Chevrolet Chevy Express G3500, Van Cargo Extended, 4.8 CSECTION Circuit/System Testing
- Test for less than 1.0 ohm of resistance between the DLC ground circuit terminal 5 and ground.
- If greater than the specified range, test the ground circuit for open/high resistance.
- Ignition OFF, disconnect the harness connector (splice pack comb) at JX 200. Install a 3-amp fused jumper wire between JX 200 terminal A and terminal D, harness side.
- Ignition ON, with a scan tool, attempt to communicate with the instrument panel cluster (IPC). Communication should be available.
- If no communication, test the serial data circuit for a short to ground, a short to voltage or an open/high resistance between the IPC and the DLC. If the circuit tests normal, replace the IPC.
- Install another 3-amp fused jumper wire to JX 200 terminal A, harness side.
- With IPC communications established, use the other end of the jumper wire to connect all other terminals, harness side, one at a time and verify that low speed communication remains available to the IPC.IMPORTANT: Allow communications for 5 seconds after connecting a module with the jumper to determine if communication is interrupted or not.
- If low speed communication is interrupted after connecting an individual module at JX 200, test the serial data circuit between JX 200 and the last module connected for a short to voltage and short to ground. If the circuit tests normal, replace the module that caused 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.