* Dislodged or Damaged Sending Unit: The fuel level sending unit is located within the fuel tank and is responsible for sending a signal to the gauge. During the fuel pump replacement, this unit could have been accidentally bumped, dislodged, or its wiring connector damaged. This is the most likely culprit.
* Wiring Issues: The wiring harness leading from the sending unit to the gauge can be easily damaged during the fuel pump replacement. This could be a broken wire, a loose connection, or a corroded connection. Check the wiring carefully for any damage or loose connections.
* Ground Issues: A poor ground connection in the fuel tank area or within the vehicle's electrical system can prevent the gauge from reading correctly. The repair process might have inadvertently disturbed a necessary ground.
* Fuel Pump Wiring Interferance: Although less likely, incorrect routing or accidental damage to the fuel pump's wiring during installation could also impact the gauge's functionality, especially if the wiring for the fuel pump and sending unit share a common harness.
* Faulty Gauge or Cluster: It's possible (though less probable) that the gauge itself or the instrument cluster (where the gauge is housed) failed coincidentally around the time of the repair.
* Low Fuel Level: While less likely if the gauge was working before, check the actual fuel level. A completely empty tank may cause unusual gauge behavior.
Troubleshooting Steps:
1. Check the Fuel Level Sender: This often requires dropping the fuel tank (or at least partially accessing it) to inspect the sending unit for damage and ensure its connection is secure.
2. Inspect the Wiring: Carefully examine the wiring harness running from the sending unit to the gauge for breaks, loose connections, or corrosion.
3. Check the Ground: Locate the ground wire for the fuel system and ensure it's clean and properly connected.
4. Test the Sending Unit: If you can access it, you can test the sender's resistance with a multimeter. A repair manual for your specific Silverado year and model will provide the correct resistance values at different fuel levels.
5. Test the Gauge Itself: If the sending unit and wiring seem fine, the gauge itself might be faulty. This might require testing the gauge within the cluster or replacing it.
If you're not comfortable performing these checks, take the truck to a qualified mechanic. They'll have the tools and expertise to diagnose and repair the problem efficiently and safely.
