1. Diagnosis:
* Confirm the problem: Is the fuel gauge truly inaccurate, or is there another issue (like a faulty gauge cluster or a wiring problem)? Try checking the gauge against the actual fuel level by manually measuring how much fuel is in the tank. If the gauge shows empty when the tank is full, the problem is likely the sending unit.
* Check the wiring: Before diving into the tank, inspect the wiring harness connected to the sending unit. Look for damaged wires, corrosion, or loose connections. Repairing these is simpler than replacing the sending unit.
2. Replacement (Most Likely Solution):
This is a fairly involved job requiring mechanical aptitude and the right tools. Safety is paramount; fuel is highly flammable.
Tools and Materials:
* New fuel sending unit: Make sure you get the correct part number for your specific 2005 Trailblazer engine and trim level.
* Socket set (metric): You'll need various sizes, including deep sockets.
* Wrench set (metric): For various bolts and nuts.
* Screwdrivers (Phillips and flathead): May be needed depending on your vehicle's access panel design.
* Fuel pump pliers (optional but recommended): Helps safely remove and install fuel line connections.
* Shop rags or absorbent towels: To soak up any spilled fuel.
* Safety glasses and gloves: To protect yourself from fuel and sharp parts.
* Fuel line disconnect tool (optional but recommended): To safely disconnect and reconnect the fuel lines.
* Jack and jack stands (or ramps): To safely lift the vehicle.
* Torque wrench: To properly tighten the bolts to prevent leaks.
* Drain pan: To catch any remaining fuel.
Procedure:
1. Disconnect the battery negative terminal. This prevents accidental shorts and sparks.
2. Drain the fuel tank (as much as possible). This significantly reduces the risk of fuel spills.
3. Raise and support the vehicle securely. Use jack stands and follow proper safety procedures.
4. Access the fuel pump module. This usually involves removing the rear seat or accessing a panel under the rear of the vehicle, depending on your specific Trailblazer model. Consult a repair manual for exact instructions.
5. Disconnect the electrical connector. Carefully unplug the electrical connector from the fuel sending unit.
6. Disconnect the fuel lines. Use fuel line disconnect tools if available to prevent damage and spills. Carefully cap the lines to prevent fuel leakage.
7. Remove the fuel pump module assembly. This typically involves removing retaining rings or bolts.
8. Replace the fuel sending unit. This step will vary depending on the design of your specific fuel pump module. Often, the sending unit is a separate component within the module, but sometimes it's an integrated unit. Carefully remove the old unit and install the new one.
9. Reassemble everything in reverse order. Double-check all connections, making sure the fuel lines are securely connected and the electrical connector is properly seated.
10. Lower the vehicle.
11. Reconnect the battery.
12. Top off the fuel tank.
13. Check for leaks: Before driving, inspect all connections and the surrounding area for any leaks.
14. Test the fuel gauge: Start the engine and check the gauge's accuracy.
Important Notes:
* Consult a repair manual specific to your 2005 Trailblazer. This will provide detailed instructions and diagrams tailored to your vehicle. A Haynes or Chilton manual is a good investment.
* If you're not comfortable with this repair, take it to a qualified mechanic. Working with fuel is dangerous, and improper repair could lead to serious consequences.
This is a general overview. The exact procedure will vary depending on your Trailblazer's model and year. Always prioritize safety and consult your vehicle's repair manual for specific instructions.
