Green or blue — information only
Seat belt
The driver's or a passenger's belt is not fastened. On some cars the lamp also comes on because of items on the seat: the sensor takes them for a passenger.
These lamps are not about a fault: they say a system is switched on, or remind you of something simple to do.
What to do now
- Fasten the belt — that is the only correct action.
- If everyone is belted and the lamp is on, take the bag off the front seat or put it in the boot.
- Do not silence the reminder with a buckle plug. Beyond the obvious, some cars then stop counting the passenger correctly and change how the airbag behaves.
- The buckle is a switch with a wire under the seat. Its connector gets kicked, and knocked loose when the interior is cleaned; after that the lamp stays on however you belt up.
- A pretensioner that fired in a crash also holds the lamp on and stores a code. The belt is then replaced as a whole: a «repaired» pretensioner will not fire a second time.
Codes usually behind it
The lamp only says that something is wrong. The code says what exactly — read it with an adapter and look it up here.
What to read next
A lamp is not a diagnosis. The same symbol lights up for a dozen different reasons, and only the code stored in the car tells them apart.
How the app helps
CarScan reads the codes behind the lamp through an OBD-II adapter, explains them in plain words and puts them into a report you can show to a mechanic.