- LED lamps draw less current than halogen, so body control modules may report a fault.
- Symptoms: bulb-out warnings, hyper-flash and flicker shortly after start-up.
- Fixes: load resistors, CANbus decoders or adapter harnesses — sometimes module coding.
- A good supplier states the required adapter or coding for each platform.
Modern vehicles monitor lighting circuits. When the current draw of a lamp falls outside the expected range, the body control module assumes a bulb has failed and shows a warning, flashes indicators rapidly or switches the circuit off. LED assemblies draw far less current than halogen bulbs, so this is the most common installation issue.
Three common symptoms
- Bulb-out warning on the dashboard after installation.
- Hyper-flash: the turn signal blinks twice as fast as normal.
- Flicker or a lamp that turns off a few seconds after start-up.
How factories solve it
Load resistors add resistance in parallel to mimic a halogen load. They are simple but generate heat and must be mounted on metal. CANbus decoders contain capacitors and logic to smooth PWM signals and are preferred for headlights. Adapter harnesses convert one connector pinout to another, for example when fitting a full-LED lamp to a halogen-equipped trim.
When coding is required
Some platforms — certain BMW, Audi and Mercedes-Benz models — need the light module coded to accept the new lamp type, especially when upgrading from halogen to factory-LED style assemblies. A reliable supplier states this clearly on the product page or quotation.
What to ask your supplier
- Is the lamp tested on a vehicle with the same trim and market?
- Which adapters or decoders are included?
- Is any coding required and with which tool?
- What happens if a warning persists after installation?
All of our assemblies are listed with their installation type, and we confirm adapters per order. Ask us for the wiring notes for your platform.
Need help with your range? Send us your vehicle list or browse our led headlight assemblies.
