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 MANUALSPONTIAC2008GRAND PRIX BASEREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 252 (FIXED AND MOVEABLE WINDOWS)DIAGNOSTIC INFORMATION AND PROCEDURESDTC B0283CIRCUIT/SYSTEM TESTING
2008 Pontiac Grand Prix Base
Circuit/System Testing
2008 Pontiac Grand Prix BaseSECTION Circuit/System Testing
WARNING: This page is about a different car, the 2008 Hummer H2. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, disconnect the REAR DEFOG relay.
- Test for less than 1.0 ohm between the ground circuit terminal 85 and ground.
- If greater than the specified range, test the relay coil ground circuit for an open/high resistance.
- Connect a test lamp between the control circuit terminal 86 and the ground circuit terminal 85.
- Ignition ON, command the defogger grid ON and OFF by pressing and depressing the rear defogger switch. 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 HVAC control module.
- 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 HVAC control module.
- If all circuits test normal, test or replace the REAR DEFOG 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:
- • 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.