Symptom
Headlights not coming on
One or both headlights fail to light, or the automatic setting no longer switches them on as the light fades. Both lamps failing at once is the useful case, because two bulbs almost never die together — that points at the module or the supply that drives them rather than at the lamps. Cars with automatic lighting add a second possibility that catches people out: the light sensor sits at the top of the windscreen, and a sunshade, a dashcam mount or a heavily tinted screen strip can leave the car convinced it is still daylight.
Also described as: headlights not working, no headlights, lights wont come on, dipped beam not working, automatic lights not working, چراغ جلو روشن نمیشود, نور پایین کار نمیکند, no encienden faros, luces no encienden, faros no funcionan, الكشافات تضوي, الأنوار تولع, الكشافات تنور, الأنوار الأمامية تنور, اللمبات الأمامية مطفية
What this usually means
Both lamps failing at once is the useful case, because two bulbs almost never die together — that points at the module or the supply that drives them rather than at the lamps. One lamp out is a bulb, its holder or its connector; two lamps out is upstream.
Cars with automatic lighting add a second possibility that catches people out: the light sensor sits at the top of the windscreen, and a sunshade, a dashcam mount or a heavily tinted screen strip can leave the car convinced it is still daylight. That is not a fault at all, and it is diagnosed by switching the lights on manually — if they work, the sensor's view is the problem.
On modern vehicles the lamps are driven by a module rather than switched directly, so a failure can be the module, its supply, its earth, or the command from the light switch. Reading whether the module has been asked to light them separates the request from the delivery.
LED and xenon units change the economics. An LED headlamp is usually a sealed assembly, so a failure means the unit rather than a bulb; a xenon unit has a ballast and an igniter that fail more often than the bulb does, and both are far cheaper than the assembly.
Check the dip and main beam separately, because they often use different circuits or different elements — a car with main beam and no dip is reporting a circuit rather than a lamp.
And a headlamp that works but points at the ground has its own entry — a levelling fault rather than an electrical one.
Working through it
| What you find | Likely cause | How to confirm it | What fixes it |
|---|---|---|---|
| Both headlights out at once | Upstream — the module, its supply, an earth, or the switch command | Two bulbs almost never fail together. Check the fuse and whether the module has been commanded to light them. | Repair the supply, earth or module. Do not fit bulbs for this. |
| One lamp out | That bulb, its holder, or its connector | Swap the bulb side to side: if the fault follows, it is the bulb; if it stays, it is the circuit. | Renew the bulb, or repair the holder and connector — corrosion there is common. |
| Automatic lighting no longer switches on at dusk, manual works | The light sensor's view — a sunshade, a dashcam mount, or a tinted screen strip | Manual operation working is the discrimination. Look at what is in front of the sensor at the top of the screen. | Clear the sensor's view. No repair if that resolves it. |
| Main beam works, dip does not — or the reverse | A circuit or element rather than a lamp, since they are often separate | Test both deliberately. Partial function names the circuit. | Repair the affected circuit or renew the dual-filament bulb. |
| Xenon lamp flickers, changes colour, or fails intermittently | The ballast or igniter rather than the bulb — both fail more often and cost far less than the assembly | Swap the ballast side to side where accessible. A fault that follows names it. | Renew the ballast or igniter. Do not condemn a xenon assembly before testing these. |
| LED unit partly dark | The assembly on most vehicles — LEDs are not separately replaceable | Establish whether the vehicle uses a serviceable module or a sealed unit. | Renew the assembly, or the LED module where the design allows it. |
-
Both headlights out at once
- Likely cause
- Upstream — the module, its supply, an earth, or the switch command
- How to confirm it
- Two bulbs almost never fail together. Check the fuse and whether the module has been commanded to light them.
- What fixes it
- Repair the supply, earth or module. Do not fit bulbs for this.
-
One lamp out
- Likely cause
- That bulb, its holder, or its connector
- How to confirm it
- Swap the bulb side to side: if the fault follows, it is the bulb; if it stays, it is the circuit.
- What fixes it
- Renew the bulb, or repair the holder and connector — corrosion there is common.
-
Automatic lighting no longer switches on at dusk, manual works
- Likely cause
- The light sensor's view — a sunshade, a dashcam mount, or a tinted screen strip
- How to confirm it
- Manual operation working is the discrimination. Look at what is in front of the sensor at the top of the screen.
- What fixes it
- Clear the sensor's view. No repair if that resolves it.
-
Main beam works, dip does not — or the reverse
- Likely cause
- A circuit or element rather than a lamp, since they are often separate
- How to confirm it
- Test both deliberately. Partial function names the circuit.
- What fixes it
- Repair the affected circuit or renew the dual-filament bulb.
-
Xenon lamp flickers, changes colour, or fails intermittently
- Likely cause
- The ballast or igniter rather than the bulb — both fail more often and cost far less than the assembly
- How to confirm it
- Swap the ballast side to side where accessible. A fault that follows names it.
- What fixes it
- Renew the ballast or igniter. Do not condemn a xenon assembly before testing these.
-
LED unit partly dark
- Likely cause
- The assembly on most vehicles — LEDs are not separately replaceable
- How to confirm it
- Establish whether the vehicle uses a serviceable module or a sealed unit.
- What fixes it
- Renew the assembly, or the LED module where the design allows it.
Codes that produce this symptom (18)
Listed with the codes that most typically present this way first — the likeliest place to start.
- U0180 Lost Communication With Automatic Lighting Control Module Typical of this code Moderate
- U0181 Lost Communication With Headlamp Leveling Control Module A Typical of this code Moderate
- U0182 Lost Communication With Lighting Control Module — Front Typical of this code Moderate
- U0183 Lost Communication With Lighting Control Module — Rear A Typical of this code High
- U0241 Lost Communication With Headlamp Control Module A Typical of this code High
- U0242 Lost Communication With Headlamp Control Module B Typical of this code High
- U0252 Lost Communication With Lighting Control Module — Rear B Typical of this code High
- U0273 Lost Communication With Lighting Driver Control Module A Typical of this code High
- U0274 Lost Communication With Lighting Driver Control Module B Typical of this code High
- U0275 Lost Communication With Lighting Driver Control Module C Typical of this code High
- U0481 Invalid Data Received From Automatic Lighting Control Module Typical of this code Moderate
- U0482 Invalid Data Received From Headlamp Leveling Control Module A Typical of this code Moderate
- U0483 Invalid Data Received From Lighting Control Module — Front Typical of this code Moderate
- U0484 Invalid Data Received From Lighting Control Module — Rear A Typical of this code High
- U0542 Invalid Data Received From Headlamp Control Module A Typical of this code Moderate
- U0543 Invalid Data Received From Headlamp Control Module B Typical of this code Moderate
- U054B Invalid Data Received From Interior Lighting Control Module A Typical of this code Low
- U0553 Invalid Data Received From Lighting Control Module - Rear B Typical of this code Moderate
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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