You turn the headlight switch on your Ford F-150, but nothing happens in the back. No tail lights. No license plate illumination. Yet your brake lights, turn signals, and headlights work perfectly. This is one of the most common electrical issues across Ford F-150 model years, and it is frustrating. The good news? Most of these problems can be fixed in under an hour and for less than $20. This guide provides a step-by-step approach to diagnosing and repairing Ford F-150 tail lights not working, covering everything from blown fuses to Body Control Module lockouts.
This guide covers all model years from 2010 to 2017 and beyond. We will start with the simplest fixes and move to advanced diagnostics.
Check Fuse F-22 First
The first and most critical step in diagnosing non-working tail lights is checking fuse F-22. This fuse is the primary power source for your F-150’s rear running lights, tail lights, and license plate lights.
Why F-22 Matters Most
In many model years, especially 2010 through 2014, Fuse F-22 in the passenger-compartment fuse panel controls the entire tail light circuit. A single blown fuse disables all rear running lights, even if bulbs, wiring, and switches are perfect.
The location is the interior fuse box on the driver side dash, left of the steering wheel. The amperage is typically 10A or 15A. You should verify this via the fuse box lid diagram. The symptom match is when all tail lights and license plate lights are out, but brake lights, turn signals, and headlights still work.
Test the Fuse Properly
A fuse can appear intact but still be internally broken. Visual inspection is unreliable. Here is how to test Fuse F-22:
- Turn the headlight switch to ON.
- Use a test light or multimeter.
- Probe both metal ends of the fuse.
- If no power on either side, check wiring to the fuse box.
- If power on one side only, the fuse is blown.
- If power on both sides, the fuse is good. Move to the next step.
Pro tip: Swap F-22 with a known-good fuse of the same amperage, such as the horn fuse, to confirm the issue.
Replace with an identical fuse if blown. The cost is less than $1, and this single fix resolves the issue in over 40% of cases.
Replace Tail Light Bulbs
Many owners skip bulb replacement, assuming both cannot fail at once. But dual failure does happen, and bulbs often fail in ways you cannot see.
Bulbs That Look Good Can Be Bad
Approximately 35% of bulbs that appear intact are actually faulty. Filaments can sag, oxidize, or break microscopically. Corrosion on the base prevents proper contact.
Bulb types by model year include:
– 2010 to 2014: 3157 dual-filament bulbs
– 2015 and newer: Often 3057 or LED assemblies. Verify in your owner’s manual.
How to Replace the Bulbs
- Open the tailgate.
- Remove the screws, usually 8mm, securing the lens.
- Pull the housing out slightly and twist the bulb socket counterclockwise.
- Inspect the socket for corrosion or melted plastic.
- Insert the new bulb and reassemble.
The cost is $8 to $15 for a 2-pack from Amazon or AutoZone. Always replace in pairs, even if one side looks okay. This prevents future imbalance and ensures consistent brightness.
Test for Power and Ground at the Socket
If fuses and bulbs are good but lights still do not work, test the tail light socket directly.
What You Will Need
You will need a 12V test light or multimeter and access to the rear light assembly.
Step-by-Step Socket Test
- Turn the headlight switch ON.
- Back-probe the power terminal in the socket. Use a paperclip or back-probe tool. You should read approximately 12 volts.
- Test the ground terminal. Connect the multimeter black lead to the chassis. Touch the red lead to the ground pin in the socket. Resistance should be less than 0.5 ohms.
The results will tell you what to do next:
– If you have power and ground, replace the bulb or socket.
– If you have no power, check the relay, wiring, or switch.
– If you have no ground, fix the shared ground point.
This test eliminates guesswork. If you have power and ground but no light, the bulb or socket is faulty.
Fix the Shared Ground Connection
Tail lights and license plate lights share a common ground wire. One bad ground can kill the entire circuit.
Where to Find the Ground
The ground is located near the spare tire mount or frame rail under the rear of the truck. It appears as a black wire with a ring terminal bolted to metal. The common issue is corrosion, a loose bolt, or paint under the contact point.
How to Repair the Ground
- Disconnect the battery negative terminal.
- Remove the ground bolt.
- Sand the metal surface until it is shiny.
- Use a star washer to bite into the metal.
- Reattach the ground and tighten securely.
- Apply dielectric grease to prevent future corrosion.
Visual clue: Greenish residue or rust around the bolt indicates a bad ground.
After repair, retest the tail lights. This fix resolves persistent no-light issues even with good fuses and bulbs.
Inspect the Parking Light Relay
If you drive a 2015 through 2017 F-150, the problem may not be a fuse. It could be the parking light relay.
Why Relays Fail
Relays control power delivery. They can fail internally even if they look fine.
The location is the engine bay fuse box, also called the battery junction box, behind the 12V battery. The position is the right column, middle slot. Refer to the lid diagram for exact placement. The symptom is that fuses are good, bulbs are new, but no tail lights.
How to Test the Relay
- Locate the relay using the diagram on the fuse box lid.
- Remove the suspect relay.
- Swap with a known-good identical relay, such as the horn or A/C relay.
- Turn on the headlights and check the tail lights.
If lights work after the swap, replace the faulty relay. The cost is $15 to $30.
Do not assume the relay is good. Substitution is the only reliable test.
Unplug the Trailer Wiring Harness
Aftermarket trailer wiring is a silent killer of tail light circuits.
How It Causes Failure
Poor installation can cause back-feed, short circuits, or ground loops. It affects the running light circuit only, so brake and turn signals often still work.
Quick Diagnostic Step
- Locate the trailer harness connector, usually under the rear bumper or behind the bumper panel.
- Unplug it completely.
- Retest the tail lights.
In approximately 25% of unexplained failures, tail lights come back on after unplugging the trailer harness.
The solution is to replace with a diode-isolated harness or use the factory tow package. Never splice directly into factory wiring. Use plug-and-play adapters only.
Diagnose Headlight Switch Failure
The headlight switch activates the tail lights. If it fails, power never reaches the rear.
Signs of a Bad Switch
Tail lights work only when the switch is jiggled. There may be intermittent operation. There may be no tail lights, but brake and turn signals work.
This is most common in 2011 and earlier F-150 models.
How to Test the Switch
- Operate the switch repeatedly.
- Listen for internal clicks.
- Monitor tail light behavior.
- If there is flickering or delayed response, suspect the switch.
Repair requires steering column disassembly. Replacement parts cost $70 to $150. The time required is 1 to 2 hours.
Consider this only after ruling out fuses, relays, and wiring.
Rule Out BCM Lockout
Modern F-150s, model year 2011 and newer, use a Body Control Module that protects circuits using Field Effect Transistors. If it detects a short or high resistance, it shuts off power permanently, even after fixing the problem.
Classic BCM Lockout Signs
Tail lights flash briefly when unlocking, due to passive lighting. But they will not stay on when headlights are turned on. New bulbs, good fuses, but no light. There are no DTCs with basic code readers.
A stored code example is B132B, which indicates a short-to-ground on the left rear circuit. This is common in 2011 models.
How to Reset the BCM
Option one is using an OBD2 scan tool. Use a Ford-compatible scan tool such as Forscan or IDS. Read and clear lighting DTCs. This is an instant fix if the code was the cause.
Option two is the battery reset, which requires no tools:
1. Disconnect both battery terminals.
2. Join the positive and negative cables together using insulated pliers or a clamp.
3. Wait at least 30 minutes. Shorter resets may fail.
4. Reconnect the battery.
This forces the BCM to reset and re-enable protected circuits.
Inspect Wiring and Connectors
Physical damage to wiring is a top cause, especially in trucks with hitches, trailers, or rodent activity.
High-Risk Areas
The tailgate harness suffers repeated flexing that breaks wires. Under-bed wiring is exposed to road debris. The cab-to-bed connector is under the rear cab and prone to moisture. Near the spare tire, rodents love to nest.
How to Inspect
- Lower the spare tire for access.
- Follow the harness from the tail lights toward the cab.
- Look for cracked insulation, green corrosion from oxidized copper, chew marks from rodents, and loose or unseated connectors.
Repair Damaged Wires
- Cut out the damaged section.
- Splice with heat-shrink butt connectors.
- Seal with liquid electrical tape or conduit.
Pro tip: Wiggle wires while the lights are on and watch for flickering. If lights flicker during the wiggle test, you have found the break.
Prevent Future Failures
Tail light issues often return without preventive care. Here is how to stop them for good.
6-Month Maintenance Checklist
Perform these tasks regularly:
– Test all rear lights, including tail, brake, turn, and hazard.
– Inspect wiring near the hitch and tailgate.
– Clean bulb sockets and apply dielectric grease.
– Check ground connection tightness.
– Verify trailer harness integrity.
Protective Upgrades
Apply dielectric grease to all bulb bases and connectors. Seal exposed connectors with rubber boots. Install rodent mesh around vulnerable harness areas. Use plug-and-play trailer harnesses and never splice.
These small steps prevent 80% of recurring issues.
When to See a Mechanic
DIY fixes work in most cases, but some situations require professional help.
Seek Help If
- Power is at the fuse but no voltage at the socket.
- The ground is solid but there is no illumination.
- You suspect a BCM reflash is needed.
- Multiple lighting systems fail together.
- A TSB or recall applies to your VIN.
- DTCs like B132B will not clear.
Dealerships have Ford IDS and FDRS software to reprogram modules after repairs. This is something most DIYers cannot do.
Check your VIN at ford.com/support for free recall repairs.
Frequently Asked Questions About Ford F-150 Tail Lights Not Working
Why do my tail lights work when I unlock my truck but not when I turn on the headlights?
This is a classic sign of a BCM lockout. The Body Control Module detects high resistance in the tail light circuit and shuts off power to protect it. The unlock feature uses a low-current mode that still works. You need to clear the fault code or perform a 30-minute battery reset.
Can a bad trailer wiring harness really cause tail light failure?
Yes. Approximately 25% of unexplained tail light failures are caused by aftermarket trailer wiring. Poor installation causes back-feed or ground loops that disrupt the running light circuit. Unplugging the trailer harness is a quick diagnostic step.
How do I know if my F-150 has a BCM issue versus a simple electrical problem?
If you have replaced bulbs, verified good fuses, tested for power and ground at the socket, and the lights still do not work, the BCM is likely the culprit. Look for the symptom where tail lights flash during unlock but fail when headlights are turned on. This pattern points to BCM protection logic.
Is it worth replacing both tail light bulbs at once?
Yes. Approximately 35% of bulbs that appear intact are actually faulty. Replacing both ensures consistent brightness and prevents the problem from returning soon. The cost is minimal, at $8 to $15 for a 2-pack.
What is fuse F-22 and where is it located?
Fuse F-22 is the primary power source for tail lights, running lights, and license plate lights on many F-150 model years. It is located in the passenger-compartment fuse panel on the driver side dash, to the left of the steering wheel. It is typically a 10A or 15A fuse.
Key Takeaways for Fixing Ford F-150 Tail Lights
Ford F-150 tail lights not working is almost always a simple fix involving the fuse, bulb, ground, or relay. Start with fuse F-22, which resolves over 40% of cases. Test power and ground at the socket before replacing anything else. On 2011 and newer models, do not overlook BCM lockout, which requires a 30-minute battery reset or scan tool to clear fault codes. With the right tools and method, you will have your lights back tonight for under $20.
