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 MANUALSCHEVROLET2006CHEVY EXPRESS G2500, VAN CARGO, 6.6 2REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1091 (LIGHTING SYSTEMS)DIAGNOSTIC INFORMATION AND PROCEDURESHIGH MOUNT STOP LAMP MALFUNCTIONCIRCUIT/SYSTEM TESTING
2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2
Circuit/System Testing
2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2SECTION Circuit/System Testing
WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, disconnect the X5 harness connector at the underhood fuse block.
- Connect a test lamp between the CHMSL relay control circuit terminal K6 and ground at the harness connector.
- Apply the brake pedal ON and OFF. The test lamp should turn ON and OFF when changing between the commanded states.
- If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
- If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
- Ignition OFF, reconnect the X5 harness connctor to the underhood fuse block. Disconnect the harness connector at the center high mounted stop lamp (CHMSL).
- Test for less than 1.0 ohm of resistance between the ground circuit terminal B and ground.
- If greater than the specified range, test the ground circuit for and open/high resistance.
- Connect a test lamp between the CHMSL control circuit terminal A and ground.
- Apply the brake pedal ON and OFF. The test lamp should turn ON and OFF when changing between the commanded states.
- If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the underhood fuse block.
- If the test lamp is always OFF and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, replace the underhood fuse block.
- If the test lamp is always OFF and the circuit fuse is open, test the control circuit for an short to ground. If the circuit tests normal, replace the CHMSL.
- If all circuits test normal, test or replace the CHMSL.
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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.