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 PASSENGER EXTENDEDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 503 (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 G3500, Van Passenger Extended
Testing the Serial Data Circuits for an Open/High Resistance
2008 Chevrolet Chevy Express G3500, Van Passenger ExtendedSECTION Testing the Serial Data Circuits for an Open/High Resistance
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2009 GMC Savana Special, 2009 GMC Savana Camper Special, 2009 GMC Savana, 2009 Chevrolet RV Cutaway, and 2009 Chevrolet Cutaway. 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.