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 1616 (DATA COMMUNICATION SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESSCAN TOOL DOES NOT COMMUNICATE WITH HIGH SPEED GMLAN DEVICECIRCUIT/SYSTEM TESTINGTESTING THE SERIAL DATA CIRCUITS FOR AN OPEN/HIGH RESISTANCE
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6
Testing the Serial Data Circuits for an Open/High Resistance
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Testing the Serial Data Circuits for an Open/High Resistance
WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, disconnect the harness connectors with the high speed GMLAN serial data circuits at an easily accessible control module that is not communicating.
- Ignition OFF for 60 seconds, test for greater than 100k Ξ© between each pair of serial data circuits at the control module connector that was just disconnected. Verify that one pair of serial data circuits are greater than 100k Ξ©.
- If each pair of serial data circuits is less than the specified range, replace the control module that was disconnected.
- Connect the harness connectors at the control module that was disconnected.
- Disconnect the harness connectors with the high speed GMLAN serial data circuits at another control module, in the direction of the open circuit.
- Ignition OFF for 60 seconds, test for greater than 100k Ξ© between each pair of serial data circuits at the control module connector that was just disconnected. Verify that one pair of serial data circuits are greater than 100k Ξ©.
- If each pair of serial data circuits is less than the specified range, replace the control module that was just disconnected.
- Repeat step 3 until one of the following conditions are isolated:
- An open/high resistance on the serial data circuit between 2 control modules
- An open/high resistance on the serial data circuit between a control module and a terminating resistor
- An open/high resistance terminating resistor
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- β’ You smell fuel, burning insulation, or see smoke.
- β’ Brakes feel soft, pull hard to one side, or make grinding noises.
- β’ The engine overheats, stalls repeatedly, or misfires under load.
- β’ You are missing required tools, torque specs, or safe lifting equipment.
- β’ You are not confident in the next step or safety outcome.