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 1447 (DATA COMMUNICATION SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESSCAN TOOL DOES NOT COMMUNICATE WITH HIGH SPEED GMLAN DEVICECIRCUIT/SYSTEM TESTINGDIAGNOSTIC 2
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6
Diagnostic 2
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Diagnostic 2
WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
- Connect the harness connector at the TCC module.
- Ignition OFF, disconnect the harness connector the ECM.
- Ignition ON, attempt to communicate with the VCIM. Communication should not be available.
- If communication is established, replace the ECM.
- Ignition OFF, disconnect the harness connector at the transmission control module (TCM).
- Ignition ON, attempt to communicate with the VCIM. Communication should not be available.
- If communication is established, test the following serial data circuits between the ECM and the TCM for a short between the circuits, short to ground or a short to voltage. If the circuits test normal replace the EBCM.
- Terminal 13
- Terminal 14
- If communication is established, test the following serial data circuits between the ECM and the TCM for a short between the circuits, short to ground or a short to voltage. If the circuits test normal replace the EBCM.
- Ignition OFF, disconnect the harness connector at the electronic brake control module (EBCM).
- Ignition ON, attempt to communicate with the VCIM. Communication should not be available.
- If communication is established, test the following serial data circuits between the TCM and the EBCM for a short between the circuits, short to ground or a short to voltage. If the circuits test normal replace the EBCM.
- Terminal 24
- Terminal 37
- If communication is established, test the following serial data circuits between the TCM and the EBCM for a short between the circuits, short to ground or a short to voltage. If the circuits test normal replace the EBCM.
- Ignition OFF, disconnect the harness connector at the headlamp leveling module.
- Ignition ON, attempt to communicate with the VCIM. Communication should not be available.
- If communication is established, test the following serial data circuits between the EBCM and the headlamp leveling module for a short between the circuits, short to ground or a short to voltage. If the circuits test normal replace the headlamp leveling module.
- Terminal 7
- Terminal 8
- If communication is established, test the following serial data circuits between the EBCM and the headlamp leveling module for a short between the circuits, short to ground or a short to voltage. If the circuits test normal replace the headlamp leveling module.
- Ignition OFF, disconnect the X1 harness connector at the pedestrian impact protection (PIP) module.
- Ignition ON, attempt to communicate with the VCIM. Communication should not be available.
- If communication is established, test the following serial data circuits between the PIP module and the headlamp leveling module for a short between the circuits, short to ground or a short to voltage. If the circuits test normal replace the PIP module.
- Terminal 35
- Terminal 37
- If communication is established, test the following serial data circuits between the PIP module and the headlamp leveling module for a short between the circuits, short to ground or a short to voltage. If the circuits test normal replace the PIP module.
- Ignition OFF, disconnect the X1 harness connector at the TCC module.
- Ignition ON, attempt to communicate with the VCIM. Communication should not be available.
- If communication is established, test the following serial data circuits between the TCC module and the PIP module for a short between the circuits, short to ground or a short to voltage. If the circuits test normal replace the TCC module.
- Terminal 7
- Terminal 8
- If communication is established, test the following serial data circuits between the TCC module and the PIP module for a short between the circuits, short to ground or a short to voltage. If the circuits test normal replace the TCC module.
- Ignition OFF, disconnect the harness connector at the BCM.
- Ignition OFF, test for infinite resistance between the following serial data circuits of BCM and ground.
- Terminal 8
- Terminal 9
- If less than the specified value, test the serial data circuit for a short to ground.
- Ignition ON, test for less than 1-volt between the following serial data circuits of BCM and ground.
- Terminal 8
- Terminal 9
- If greater than the specified range, test the serial data circuit for a short to voltage.
- Ignition OFF, test for infinite resistance between the BCM serial data circuit terminals 8 and 9.
- If less than the specified value, test for a short between the serial data circuits.
- If all circuits test normal, replace the BCM.
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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.