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 MANUALSCHEVROLET2006SUBURBAN C1500, 5.3 ZREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1681 (LIGHTING SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC B2585CIRCUIT/SYSTEM TESTING
2006 Chevrolet Suburban C1500, 5.3 Z
Circuit/System Testing
2006 Chevrolet Suburban C1500, 5.3 ZSECTION Circuit/System Testing
WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, disconnect the park lamp relay.
- Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
- If the test lamp illuminates, test the control circuit for a short to voltage.
- Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.
- If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
- Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
- If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
- Disconnect the harness connector at the appropriate park lamp.
- Test for less than 5 Ξ© between the ground circuit terminal listed below and ground:
- Park/Turn Signal Lamp - Terminal G
- Tail/Stop and Turn Signal Lamp - Terminal GRD
- License Lamp - Terminal B
- Rear Fender Clearance Lamp - Terminal B
- Side Marker Lamp - Terminal A
- Roof Clearance Lamp - Terminal A
- Tailgate Marker Lamp - Terminal B
- If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
- Connect the harness connector at the park lamp.
- Connect a 15 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the park lamp is activated.
- If the park lamp does not activate and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the park lamp.
- If the park lamp does not activate and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or replace the park lamp.
- Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
- Command the Parking Lamps ON and OFF with a scan tool. 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 ground. If the circuit tests normal, replace the BCM.
- If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
- If all circuits test normal, replace the park lamp relay.
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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.