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 1
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6
Diagnostic 1
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Diagnostic 1
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.
- Remove the terminator resistor.
- Test for 108-132 ohms of resistance between terminals A and B of the terminator resistor.
- If not within the specified range, replace the resistor.
- Connect the harness connector at the terminator resistor.
- Ignition OFF, disconnect the X3 harness connector at the BCM.
- Ignition OFF, test for less than 2 ohms of resistance between the DLC serial data circuit terminal 6 and BCM serial data circuit terminal 16.
- If greater than the specified range, test the serial data circuit for open/high resistance.
- Ignition OFF, disconnect the X4 harness connectors at the BCM.
- Test for less than 5 ohms of resistance between the following ground circuit terminals and ground.
- X3 terminal 1
- X3 terminal 5
- X4 terminal 9
- If greater than the specified range, test the ground circuit for an open/high resistance.
- Ignition ON, verify a test lamp illuminates between the following B+ circuit terminals and ground.
- X2 terminal 2
- X3 terminal 2
- X3 terminal 3
- X4 terminal 1
- X4 terminal 2
- X4 terminal 3
- X4 terminal 4
- X4 terminal 10
- If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, also test the B+ output circuits for a short to ground.
- Ignition OFF, test for infinite resistance between the following serial data circuits of the DLC and ground.
- Terminal 6
- Terminal 14
- If less than the specified value, test the serial data circuits for a short to ground.
- Ignition ON, test for less than 1-volt between the following serial data circuits of the DLC and ground.
- Terminal 6
- Terminal 14
- If greater than the specified range, test the serial data circuit for a short to voltage.
- Ignition OFF, test for infinite resistance between the DLC serial data circuit terminal 6 and terminal 14.
- If less than the specified value, test for a short between the serial data circuits.
- Connect the X3 and X4 harness connector at the BCM.
- Ignition OFF, disconnect the harness connector at the VCIM.
- Ignition ON, attempt to communicate with the TCC module. Communication should not be available.
- Replace the VCIM.
- Ignition OFF, disconnect the harness connector at the noise filter.
- Ignition ON, attempt to communicate with the TCC module. Communication should not be available.
- If communication is established, test the following serial data circuits between the noise filter and the VCIM, and the noise filter and the terminator resistor for a short between the circuits, short to ground or a short to voltage. If the circuits test normal, replace the noise filter.
- Noise filer terminal 3 VCIM terminal 28
- Noise filter terminal 4 VCIM terminal 14
- Noise filter terminal 3 and terminal 4
- Noise filter terminal 3 terminator resistor terminal A
- Noise filter terminal 4 terminator resistor terminal B
- If communication is established, test the following serial data circuits between the noise filter and the VCIM, and the noise filter and the terminator resistor for a short between the circuits, short to ground or a short to voltage. If the circuits test normal, replace the noise filter.
- Ignition OFF, disconnect the X3 harness connector at the BCM.
- Ignition OFF, test for infinite resistance between the following serial data circuits and ground.
- Terminal 16
- Terminal 17
- 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 and ground.
- Terminal 16
- Terminal 17
- If greater than the specified range, test the serial data circuit for a short to voltage.
- Ignition OFF, test for infinite resistance between the serial data circuit terminal 16 and terminal 17.
- If less than the specified value, test for a short between the serial data circuits.
- If the 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.