CarScan
B2103Body

Exterior lighting circuit malfunction

Where to start

The exterior lighting circuit. Start with the bulb and its holder: a blown bulb causes this code more often than everything else put together. Then the fuse and the lamp connector, which fills with water. ⚠️ A special case is LED bulbs fitted in place of ordinary ones: the module watches the current in the circuit, an LED draws several times less, and the car honestly decides the bulb has blown. If the code appeared right after a bulb change, there is nothing to search for — you need load resistors or standard bulbs. Check the rear of the car with a helper: half the «faults» here turn out to be a bulb that lights but sits badly in its holder.

A code is not a diagnosis. It says which check failed, not which part to replace. Clearing it without repair only means the car will report it again in a few trips.

How to put together a report a mechanic will actually read

How the code is built

Letter — the systemBody: lights, climate, airbags
Common or the maker's ownGeneric code, second group
Number of the faultThe serial number inside that group — it does not say how serious the fault is

All codes in «Body, airbags and lighting»

How the app helps

CarScan reads this code from your car through an OBD-II adapter, shows whether it is active now or only stored, names the module that reported it, and puts it into a plain-text report for your mechanic.

See what the app does

Unfamiliar word? Open the glossary

What the letter and the four digits mean