Table of Contents
Having tail lights that don’t work properly is not just an inconvenience – it’s also illegal and extremely dangerous. Driving at night or in low visibility conditions without functioning brake lights and tail lamps puts you and others on the road at risk. So if you’ve noticed your tail lights malfunctioning or not turning on at all, you’ll want to address the issue as soon as possible.
In this comprehensive guide, we’ll walk through the common causes of non-functional tail lamps and brake lights. We’ll also provide actionable troubleshooting tips to help diagnose and resolve the problem on your own vehicle. By the end, you’ll know exactly why your tail lights aren’t working and how to get them fixed.
Key Reasons Tail Lights Not Working
There are a few key components that could cause issues resulting in faulty, dim, or non-functional tail lights:
Burnt Out Bulbs
The most straightforward reason your tail lamps aren’t working is because the dual filament bulb has burned out. Tail light bulbs contain two filaments – one for the tail lamp function and one for the brake light function. If either filament burns out, you’ll lose that aspect of the lighting. Faulty sockets, vibration, extreme temperatures, voltage spikes, and normal wear over time can all cause bulbs to burn out prematurely.
Problems with the wiring leading to the tail light assemblies could prevent the lights from turning on. Issues here include:
- Loose, damaged, or corroded connectors and ground wires
- Cracked or worn wiring insulation allowing shorts
- Partial breaks in the wires or high resistance points leading to dim or intermittent function
Such wiring faults disrupt the power supply from the battery and lighting control systems from properly powering on the tail lamps.
Blown electrical fuses are one of the most common reasons tail lights malfunction. Fuses help protect against excessive current draw. But when they blow, they cut power flow completely to the downstream lighting systems. Start by inspecting the tail light fuse first. Also check fuses linked to critical systems like the brake pedal position sensor, lighting and dimmer controls, and body control modules.
Faulty Brake Light Switch
The brake light switch activates when you depress the brake pedal to illuminate the brake lamps. If this switch malfunctions or fails entirely, your brake lights can stop responding properly to pedal input even if the tail lamps still function. Faults here prevent the signal from the pedal from reaching the control module to activate the brake lights.
Bad Lighting Control Module
Modern vehicle lighting systems utilize computer control modules to manage functions like dimming, automatic light activation, and turning signals. If a key control unit fails, it can disable components like your tail lamps even if the bulbs, fuses, and wiring check out. Scan for diagnostic trouble codes (DTCs) to detect bad lighting and body control module issues.
Now that we’ve covered the most common culprits, let’s go through systematic troubleshooting procedures to properly diagnose and resolve your non-working tail lights.
Step-by-Step Troubleshooting Process for Tail Light Fuse Issues
With basic automotive tools and repair knowledge, you can carry out thorough troubleshooting yourself to get your tail lamps working again. Here are the key steps:
1. Visual Inspection
Start by visually inspecting all tail light assemblies from inside and outside the vehicle. Look for any external damage, cracks, or moisture intrusion which could cause issues. Check that the brake pedal fully releases and resets when not pressed. Also verify that the brake fluid reservoir level falls between the MIN and MAX lines. Low fluid levels could indicate external brake system leaks that might impact brake lamp function.
Next, have an assistant step on the brake pedal while you observe the tail lamp operation from outside the rear of the vehicle. This allows you to isolate brake and tail lamp circuits. Check that running lights and turn signals still activate properly as well.
2. Check Bulb Condition
If one or more tail lamps don’t activate during the brake pedal tests, inspect the non-working light assembly. Remove each bulb by accessing the housing and twisting counterclockwise. Look for a damaged or worn bulb filament, black residue, white powder deposits or a greenish tint indicating a bad bulb no longer making solid electrical contact. Always handle new bulbs carefully by the base and never touch the glass with bare fingers which shortens lifespan from hand oil residue.
3. Verify Fuse Integrity
Using a fuse circuit tester, check continuity across tail light system fuses in the under hood and cabin fuse boxes. Also inspect visually for a broken filament inside transparent fuses indicating an open circuit. Test all associated brake, taillight, body control, and lighting management fuses one by one. Replace any blown fuses with the same amperage rating to restore power flow.
4. Inspect Wiring Condition
If replacing the bulb and fuse doesn’t resolve the problem, faulty wiring could be preventing current flow. Check connectors unplugged from the tail lamp housing for dirt buildup or corrosion on the terminals. Such debris increases resistance which lowers voltage passed to the lights.
Also, inspect wires leading from the housing into the body panels for cracking, chafing, splicing, or other physical damage. If any wiring damage exists, the entire affected harness section will need splice repair or complete replacement.
5. Test Voltage at Electrical Connectors
Using a digital multimeter, test voltage at each tail light assembly wiring harness. Turn the ignition to RUN while having an assistant hold down the brake pedal. Check voltage output at the vehicle battery to confirm at least 12V. Then connect the meter probes at the tail lamp harness plugs. Proper voltage here with non-working lights points to a bad ground connection. No voltage means there’s a wiring fault or blown fuse cutting off the power source.
6. Verify Proper Electrical Ground
Complete loss of tail lamp function in multiple or all lights often results from loss of the ground connection feeding the lighting system. Unbolt the tail lamp assembly and disconnect the wires. Use a multimeter to check for continuity between the ground wire and bare vehicle metal. No continuity means the ground wire or bonding point is damaged and must be repaired or replaced.
7. Scan for Diagnostic Trouble Codes
If all wiring, fuses, bulbs, switches, and grounds check out fine, a deeper electrical issue exists. Retrieve any diagnostic trouble codes (DTCs) stored in onboard computers related to exterior lighting systems. Body control, smart junction box, tail lamp control, and brake system modules may show faults interfering with proper light operation. DTCs point to specific components needing replacement – like a bad brake light switch or faulty control module.
Following these troubleshooting procedures methodically helps trace tail light operation issues back to their root cause – whether it’s simply a bad bulb or more complex electrical faults. But if you still can’t get your tail lamps working after complete inspection and testing, then it’s time to take your vehicle into a professional shop. Describe in detail all troubleshooting steps you’ve carried out to help the technician efficiently continue diagnosing the specific problem. Most tail lamp issues can be resolved affordably with some time and auto electrical troubleshooting know-how.
We hope this complete troubleshooting guide gives you confidence tackling that frustrating tail light problem yourself. But if any questions come up during testing or repair, don’t hesitate to bring your vehicle into a professional auto shop like ours. Describe the symptoms, tests completed, and past repair attempts clearly. We have factory-level diagnostic computers, wiring schematics, and experienced technicians to help accurately track down and resolve even the most troublesome tail lamp issues. Let us know if we can assist with getting your tail lights working reliably!
Frequently Asked Questions About Non-Functional Tail Brake Light Bulbs
To round out this comprehensive guide, let’s answer some of the most common questions drivers have about diagnosing and repairing tail lights that stop functioning properly:
What should I do if tail lights work but brake lights don’t?
Start by inspecting your brake light bulbs in each non-working housing on the vehicle. A burned out brake filament on a dual contact bulb will cut out only the brake lamp while leaving the tail lamp operational. Also check brake-specific wiring, fuses, switches, relays, and control systems as covered in the troubleshooting process above. Note any other exterior lights with brake actuation like center high mount stop lamps. Localize the failure point to brake circuitry versus standard tail lamp power feeds.
Can tail lights still work if LED strips stop functioning?
Yes – many modern vehicles integrate decorative LED light strips into tail lamp housings which are independent from the main bulb or auxiliary LED brake lamps. So the standard tail, brake, and turn signal lamps which actually provide rear visibility can still operate even if the extra LED strips burn out or malfunction internally. As long as the legally required lamps still illuminate, the vehicle remains road legal. But any LED, bulb, or socket failures in central brake or tail lamp areas will require immediate repair to restore full visibility and safety compliance.
Why does only one tail light not work but the other works fine?
Isolated operation issues affecting just one side often stem from physical bulb, connector or ground faults specific to that light assembly. Start diagnosis on the side with the non-functioning lamp(s). Tail lights use side-specific wiring running directly from the switchgear to each rear corner. So localized harness damage on one side interrupts the affected tail lamp power feed. If replacing bulbs and testing that housing’s wiring proves fine, inspect switches, relays, and modules for outputs serving only the non-working side.
Can a bad bulb cause a no tail lights fuse to blow?
It’s possible – when filaments inside old, worn out bulbs eventually break apart completely, this can short circuit the entire downstream wiring. The excessive current draw from the severe short then immediately pops the protective fuse for that lighting circuit. So if one tail light housing or section causes repeated new fuse failures, inspect bulbs carefully even if filaments appear intact. Use a multimeter to check for shorts between bulb contacts before introducing any new fuses which could potentially pop again.
Why do my brake lights work but tail lights don’t?
Since brake lamps and tail lamps in most vehicles utilize shared dual-filament bulbs, the root causes for such an isolated symptom remain similar. Start by checking for failed tail lamp filaments in all rear bulb housings even if the brake lamps still glow bright red. Also scan for any diagnostic trouble codes specifically related to exterior lighting controls which may show faults preventing tail lamp circuit activation separate from the brake lighting loop. Finally, visually trace tail lamp-specific wiring through splice points and into any isolation modules or switches to check for connector issues selectively impacting the tail lamp feed line.
How do I know if problem is in fuse box, relay, or wiring?
With basic fuse circuit testing and voltage checks, you can effectively isolate the problem:
- If tail lamp and brake lamp fuses show continuity, probe feed and ground wires at lamp sockets with a multimeter to check for power flow. No voltage means there’s an upstream wiring open circuit or bad relay.
- Voltage at socket but no tail lamp operation indicates blown bulbs or malfunctioning light housings.
- Proper voltage through all wires, fuses, sockets, and bulbs but inoperative lamps points to a bad relay, body control module or software-related lighting controls issue.
Can a bad ground cause brake lights to not work?
Definitely – with vehicles relying so heavily these days on sensitive electronics controlling lighting, a faulty ground connection can certainly disable brake lamps. And since brake lights tap into the high current main vehicle ground source, corrosion here generates excess resistance. This often drops supply voltage below levels necessary to activate brake lamp bulbs or LEDs. So poor ground integrity should be one of the first checks when chasing brake, tail, or other exterior lighting faults refusing to illuminate despite verified power feeds.
How much does it cost to fix tail lights not working?
Typical tail light repair costs range widely from $50-$350+ depending on whether it’s just a basic bulb or fuse replacement, harness wiring repair, or deeper electrical faults requiring professional diagnosis and control module reprogramming or replacements. But not addressing non-working tail lights runs legal risks and leads to extremely dangerous driving conditions that far outweigh the investment to properly restore this critical safety lighting system.