It might be one of the wires going to the lights is broke. You can easily find that by crwling under the car with a light and go up and down your wires trying to find a break in it/them.
burnt out lightbulb!
It may be the reverse light switch that need replacing, which is on the transmission.
sometimes when the lights blow out the fuse also blows out. check the fuse!!
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The reverse light sensor switch on the gearbox needs replacing. The switch is normally located on top of the gearbox & around the middle of underneath the air intake box.
Even after replacing the switch it needs to be aligned with the shifter. Put the car in reverse and then have someone watch the lights as you loosen the switch and then rotate it slightly forward or backwards. once the lights come on, secure it in position.
Try replacing the back-up light switch. It is located on the left side of the transmission. It is a common problem.
The fuse for the backup lights on a 1992 Mercedes-Benz 500SL is typically located in the fuse box, which is found under the dashboard on the driver's side. You should look for a fuse labeled for the backup lights or reverse lights, usually identified in the owner's manual. If the fuse is blown, replacing it should restore power to the backup lights. Always ensure to check the vehicle's manual for the exact fuse number and specifications.
The fuse for the reverse lights on a 2002 Toyota Avalon is typically located in the engine compartment fuse box. Look for a fuse labeled "BACK UP" or "REVERSE" in the fuse diagram found on the cover of the fuse box. If the fuse is blown, replacing it should restore the functionality of the reverse lights. Always refer to the owner's manual for specific details and fuse ratings.
It's a matter of replacing the reverse position swith in the transmission. This switch tells the computer wheter it's in neutral, or reverse and when in reverse it triggers the reverse lights.
you could have possibly bought the wrong bulbs and/or fuses. or when you were replacing them you may have damaged the wires. Also the reverse light switch may be defective.
Where is the fuse located for the reverse lights