Quick Answer
A BMW warning light is a stored fault, not a mystery. Yellow usually means book a diagnostic soon. Red, a flashing oil can, or a brake warning means stop and get it checked before you drive on. Guessing from a forum photo wastes time. A proper BMW scan reads the module that actually logged the code.
Book soon (usually yellow)
- Engine management / emissions light: misfire, lambda, swirl flaps, DPF, ignition. Drive gently and book a diagnostic.
- 4x4 / 4WD / DSC related messages: transfer case, wheel speed sensors, or a battery that is on the way out.
- Service / CBS due: oil or vehicle check interval. Book a service, not a panic diagnostic, unless something else is on.
- Battery / charging: often an ageing battery or a failing alternator. BMWs are fussy about voltage.
Stop or get it recovered (red or flashing)
If in doubt, stop. A recovery bill is cheaper than an engine.
- Red oil pressure: stop the engine. Driving it can wreck the motor.
- Red brake or ABS with a hard pedal: do not keep driving “to see if it clears”.
- Coolant red / overheat: stop. Check level only when cold.
- Airbag light after a knock: the car may not fire the bags. Book it, do not ignore it.
Why a cheap OBD plug is not enough
A £20 dongle reads a handful of powertrain codes. BMWs store faults in airbag, ABS, transfer box, mechatronic and body modules. We scan the car properly, then tell you what is urgent versus what can wait until the service.