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 290 (CELLULAR SYSTEM, ENTERTAINMENT SYSTEM, AND NAVIGATION SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESNO (OR NOISY) ONSTAR AUDIOCIRCUIT/SYSTEM TESTING
2008 Chevrolet Chevy Express G3500, Van Passenger Extended
Circuit/System Testing
2008 Chevrolet Chevy Express G3500, Van Passenger ExtendedSECTION Circuit/System Testing
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2008 GMC Yukon XL, 2008 GMC Yukon, 2008 Chevrolet Tahoe, 2008 Chevrolet Suburban, and 2008 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, disconnect the X2 harness connector at the radio and the X2 harness connector at the CIM.
- Verify that a test lamp does not illuminate between B+ and the CIM X2 harness connector terminal 1.
- If the test lamp illuminates, test the signal circuit for a short to ground.
- Verify that a test lamp does not illuminate between B+ and the CIM X2 harness connector terminal 2.
- If the test lamp illuminates, test the signal circuit for a short to ground.
- Test for less than 1 ohm between the CIM X2 harness connector terminal 1 and the radio X2 harness connector terminal 7.
- If greater than the specified range, test the circuit for a short to voltage or an open/high resistance.
- Test for less than 1 ohm between the CIM X2 harness connector terminal 2 and the radio X2 harness connector terminal 15.
- If greater than the specified range, test the circuit for a short to voltage or an open/high resistance.
- Reconnect the CIM X2 harness connector.
- Ignition ON, test for a momentary AC voltage between the signal circuit radio X2 harness connector terminal 7 and the signal return circuit terminal 15 when the white dot button on the OnStar keypad is pressed.
- If AC voltage was not present, replace the CIM.
- If all circuits test normal, replace the radio.
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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.