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 2583 (DATA COMMUNICATIONS SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC U1862CIRCUIT/SYSTEM TESTING
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6
Circuit/System Testing
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Circuit/System Testing
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2012 GMC Yukon XL, 2012 GMC Yukon, 2012 Chevrolet Tahoe, 2012 Chevrolet Suburban, and 2012 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, disconnect the harness connector X2 at the SDG module.
- Ignition OFF and the scan tool disconnected, open and close the driver door, and wait 1 minute.
- Test for less than 5.0 ohms between the ground circuit terminal 18 X2 and ground.
- If greater than the specified range, test the circuit for an open/high resistance.
- Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 8 X2 and ground.
- If the test lamp does not illuminate, test the circuit for a short to ground or an open/high resistance.
- Test for 10.5-12.5 volts between the serial data communication enable circuit terminal 16 X2 and ground.
- If less than the specified range, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the applicable communication/control module.
- Ignition OFF, connect the harness connector X2 to the SDG module.
- Ignition OFF, disconnect the harness connector X1 at the SDG module.
- Ignition ON, test for 2.1-2.5 volts between the high speed GMLAN serial data bus low circuit terminal listed below and ground:
- Terminal 15 X1
- Terminal 16 X1
- If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the applicable communication/control module.
- If less than the specified range, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the applicable communication/control module.
- If all circuits test normal, replace the SDG module.
IMPORTANT:
The scan tool must be disconnected and the ignition switch OFF for 30 seconds for proper test results.
RENDER: 1.0x
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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.