Why is only one reverse light not working?
The most common explanation is a burned-out bulb or a bad socket on the affected side.
Beyond the bulb, a variety of issues can cause only one reverse light to fail, including wiring damage, moisture intrusion, a poor ground, or a circuit-specific fuse or connector. In some models the left and right reverse lights are wired separately, so a fault on one side won’t always affect the other.
Common causes of a single reverse light failure
These are the typical culprits when only one backup light is out, helping you target the most likely fixes.
- Burned-out bulb on the affected side
- Faulty or corroded bulb socket/contact
- Damaged or loose wiring or connector in the tail light harness or near the tailgate/hinge
- Poor ground/earth connection causing intermittent or dim lighting
- LED module failure or individual LED within an LED assembly
- Moisture ingress or water exposure causing corrosion or a short
- Aftermarket wiring, adapters, or mismatched bulbs that upset the circuit
In most cases the problem points to the bulb or socket, but the issue can also be traced to wiring, grounding, or a side-specific fuse in certain makes and models.
Diagnostics and fixes
Bulb and socket check
To verify a bulb or socket issue, start with the simplest steps and work toward more involved checks.
- Turn the ignition off and gently remove the rear light assembly or access the bulb from inside the trunk, depending on your car’s design.
- Inspect the bulb for a broken filament, darkened glass, or obvious discoloration. If in doubt, swap in a fresh bulb of the same type.
- Inspect the socket for corrosion, bent contacts, or corrosion on the bulb’s tabs. Clean contacts with a contact cleaner or replace the socket if needed.
- Reinstall the bulb and test the reverse gear to see if the light now works. If it still fails, move to wiring checks.
After replacing or cleaning the bulb/socket, re-test both sides to confirm the issue is resolved.
Electrical system checks
If the bulb and socket are fine, inspect the electrical side: fuses, wiring, grounds, and connectors.
- Locate the fuse box and identify the backup/reverse light fuse or fuses in your vehicle’s manual. Check the fuse visually for a blown element or use a multimeter to confirm continuity.
- Inspect the wiring harness along the tail light assembly for damaged insulation, pinched wires, or loose connectors. Gently flex the wiring to see if the light flickers, which can indicate a loose connection.
- Check the ground connection at the tail light housing or body ground point. Clean the metal contact, tighten the mounting bolt, and ensure a solid ground path.
- Unseat and reseat the connectors at the back of the light assembly and at the wiring harness to rule out a poor connection.
- If your vehicle uses a separate control module or body computer for lighting, check for any fault codes related to the lighting circuit using an appropriate scan tool.
- After performing these checks, re-test the light in reverse. If the issue persists, consider professional inspection for more advanced faults such as a faulty body control module or hidden wiring problems.
These steps cover the majority of non-visual electrical faults and help narrow down whether the problem is a simple bulb replacement or a more complex wiring issue.
Summary
When only one reverse light fails, start with the bulb and socket, then inspect wiring, grounds, and fuses. Many failures are resolved by replacing a burned-out bulb or fixing a corroded contact, but a stubborn fault may require deeper electrical diagnosis or professional assistance. Keeping both reverse lights in good working order improves visibility and safety when reversing, and can help avoid tickets or failed safety inspections in some regions.
