U0543 code meaning
Invalid Data Received From Headlamp Control Module B
What U0543 means
Headlamp control module B is the second light controller, usually serving the headlamp opposite module A. Bentley's 2019-2020 Continental GT campaign (2056293/1) handles the two as light control left and right, at diagnostic addresses 29 and 39, and both needed new software when the outer daytime running lights failed. Jaguar's 2020 XE likewise names HCMA and HCMB (SSM74402). Which side B covers remains vehicle-specific. No public manufacturer text uses U0543; it marks data from B reaching the network in a form the receiver cannot accept. Matrix or bending light then normally falls back to a fixed low beam on the affected side, and a lighting warning appears. Swapping a headlamp without coding or running mismatched software levels left and right are typical triggers. U0242 means B is silent; A is U0542.
U0543 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.3 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0543
- Lighting system warning in the cluster
- Matrix or bending light on one side fixed to low beam
- Daytime running light on one side out
Common causes of U0543
- Most likelyDifferent or outdated software in headlamp module B compared with A
- PossibleHeadlamp B replaced without coding
- Less likelyInternal fault in headlamp module B
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Headlamp module b
What each part of U0543 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 43 | The exact fault in that area. |
What to do next
- Note U0543 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U0543
What does U0543 mean?
U0543 means "Invalid Data Received From Headlamp Control Module B". Headlamp control module B is the second light controller, usually serving the headlamp opposite module A. It is a generic code, so it means the same on every make.
Is it safe to drive with U0543?
U0543 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U0543 fail an emissions test?
U0543 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U0543 to fix?
Difficulty: medium. A typical repair takes 0.3 to 2.5 hours of work. This is a job for a workshop.
Will U0543 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.