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.
Circuit/System Testing
2004 Oldsmobile Bravada RWDSECTION Circuit/System Testing
WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, disconnect the DEFOG relay.
- Test for less than 1 ohm between the ground circuit terminal 86 and ground.
- If greater than the specified range, test the ground circuit for an open/high resistance.
- 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 30 and ground.
- If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
- Ignition OFF, disconnect the X2 harness connector at the defogger grid.
- Test for less than 5 ohms between the ground circuit terminal A and ground.
- If greater than the specified range, test the ground circuit for an open/high resistance.
- Connect the harness connector at the defogger grid.
- Ignition ON, connect a 30A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the defogger grid is activated.
- If the defogger grid does not activate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the defogger grid.
- Connect a test lamp between the control circuit terminal 85 and the ground circuit terminal 86.
- Command the Rear Defog Request 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 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 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.