* Faulty Reverse Light Switch: This is the most probable cause. The reverse light switch is often mechanically linked to the transmission and provides power to the reverse lights. If this switch is shorted or internally damaged, it could complete a circuit that inadvertently draws excessive current, blowing the fuel pump fuse. The short may only occur when the switch is activated (reverse engaged).
* Wiring Short in Reverse Light Circuit: A short in the wiring harness leading to or from the reverse lights is another possibility. Worn insulation, frayed wires, or corrosion can create a path to ground (or another energized circuit) specifically when the reverse lights are activated.
* Reverse Light Wiring Touching Fuel Pump Circuit: This is less likely but possible. If the reverse light wiring is improperly routed and comes into contact with the fuel pump wiring, it could create a short when the reverse lights are on.
* Short in the Transmission Wiring Harness: While less common, a short within the transmission's wiring harness itself could cause this issue. This is more difficult to diagnose and often requires a professional.
Troubleshooting Steps:
1. Check the Reverse Lights: When you put the car in reverse, do the reverse lights work? If not, the problem is very likely within the reverse light circuit.
2. Inspect the Reverse Light Switch: This is usually located on the transmission itself. Try to locate it and visually inspect for any signs of damage, corrosion, or burnt wires.
3. Check the Wiring: Carefully inspect the wiring harness leading to and from the reverse lights and the reverse light switch. Look for any signs of fraying, melting, or corrosion. Pay close attention to where the wiring passes near other components.
4. Test the Fuse: After addressing any visible issues, replace the blown fuel pump fuse. Try shifting into reverse again. If it blows immediately, you've narrowed down the problem to the reverse light circuit. If not, the problem is likely more complex.
5. Professional Help: If you're not comfortable working with car electrical systems, it's best to take the car to a qualified mechanic. They have the tools and expertise to properly diagnose and repair the short circuit.
Remember to disconnect the negative battery terminal before working on any car's electrical system. Safety first!
