1. Check the obvious:
* Low Transfer Case Fluid: The transfer case is crucial for AWD operation. Check the fluid level (often dipstick-accessible). Low fluid indicates leaks or a serious problem. If low, get it topped off with the correct type of fluid (consult your owner's manual).
* Fuse/Relay Problems: Check the fuses and relays related to the AWD system in your fuse box (owner's manual will show locations and diagrams). A blown fuse or faulty relay is a common and relatively easy fix.
* 4WD/AWD Switch: Ensure the 4WD/AWD switch (if your Bravada has one) is working correctly and is in the desired position. Try cycling it through positions a few times (if applicable).
* Binding Components: Check for anything binding in the drivetrain, such as a seized wheel bearing, a broken CV joint (especially if you feel vibrations or unusual noises), or other mechanical obstructions. This might require inspection underneath the vehicle.
2. More Advanced Diagnostics (may require a mechanic):
* Transfer Case Issues: Beyond low fluid, the transfer case itself might be failing (internal components worn, electrical issues within the transfer case motor). This often requires a professional diagnosis and repair.
* Actuator Problems: The actuator is an electrical component that engages and disengages the AWD system. A malfunctioning actuator can prevent the system from operating correctly.
* Wiring/Electrical Problems: Faulty wiring, connectors, or sensors can prevent the AWD system from working. This requires tracing the wiring harness and checking for shorts, broken wires, or corroded connectors. A mechanic with a wiring diagram is essential for this.
* Computer/ECM Issues: The Engine Control Module (ECM) controls many aspects of the AWD system. A faulty ECM can prevent the AWD from engaging or cause erratic behavior. Diagnosis requires specialized tools.
* Differential Problems: While less common, issues in the front or rear differential can also affect AWD operation. This requires a thorough inspection by a mechanic.
Important Considerations:
* Owner's Manual: Your owner's manual should have a section on the AWD system, including diagrams, fuse box locations, and fluid specifications.
* Professional Mechanic: If you're not comfortable working on your vehicle's drivetrain, it's best to take it to a qualified mechanic for diagnosis and repair. Improper diagnosis or repair can lead to further damage.
* Safety: Never attempt repairs while the vehicle is running. Always use jack stands and chocks for safety when working under the vehicle.
Starting with the simple checks (fluid, fuses, switch) is wise. If these don't solve the problem, professional help will be necessary to diagnose the underlying cause. Be prepared to provide your mechanic with details about when the AWD stopped working and any associated sounds or symptoms.
