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 291 (MIRROR SYSTEMS)DIAGNOSTIC INFORMATION AND PROCEDURESDTC B1640CIRCUIT/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 X3 harness connector at the appropriate door module.
- Ignition ON, verify a test lamp does not illuminate between the control circuit terminal 7 and ground.
- If the test lamp illuminates, test the control circuit for a short to voltage.
- Ignition OFF, test for infinite resistance between the control circuit terminal 7 and ground.
- If less than the specified value, test the control circuit for a short to ground. If the circuit tests normal, test or replace the applicable rearview mirror face.
- Test for 5-10 ohms of resistance between the control circuit terminal 7 and the low reference circuit terminal 3.
- If not within the specified range, test the control circuit and the low reference circuit for an open/high resistance. If the circuits test normal, test or replace the appropriate rearview mirror face.
- If all circuits test normal, test or replace the door module.
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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.