Audi A4   Controls   Instruments and warning/indicator lamps  Warning and indicator lamps
When you switch on the ignition, some of the warning and indicator lamps light up briefly to show that the associated systems are working properly. These systems are marked with a in the following tables. If one of these warning/indicator lamps does not light up, there is a fault in the associated system.
Red warning lamps

Brake system
Link

Electro-mechanical parking brake
Link

Seat belt
Link

Electro-mechanical power steering
Link

Alternator
Link

Engine oil pressure
Link

Engine oil level
Link

Cooling system
Link
AdBlue
AdBlue*
Link
AdBlue
AdBlue*
Link

Steering lock
Link

Ignition lock
Link

Speed warning*
Link

Speed warning*
Link

Adaptive cruise control*
Link
Yellow indicator lamps

Electronic stabilisation control (ESC)
Link

Electronic stabilisation control (ESC)
Link

Electronic stabilisation control (ESC)
Link

Anti-lock brake system (ABS)
Link

Safety systems
Link

Brake pads
Link

Electro-mechanical parking brake
Link

Tyre pressure*
Link

Tyre pressure*
Link

Engine management system
(petrol engines)
Link

Engine management system
(diesel engines)
Link

Emission control system
Link

Diesel particulate filter*
Link

Engine speed governing*
Link

Engine oil level
Link

Engine oil sensor
Link

Battery charge
Link

Fuel tank system
Link

Engine temperature*
Link
AdBlue
AdBlue*
Link
AdBlue
AdBlue*
Link

Washer fluid level
Link

Convenience key*
Link

Battery in remote control key
Link

Bulb monitor*
Link

Front fog lights*
Link

Rear fog light
Link

Dynamic headlight range control*
Link

Adaptive light*
Link

Light sensor/rain sensor*
Link

Active lane assist*
Link

Suspension control*
Link

Sport differential*
Link

Ignition lock
Link

Steering lock
Link

Windscreen wipers
Link

Electro-mechanical power steering, dynamic steering*
Link

Gearbox:
multitronic, tiptronic, S tronic Link

Gearbox:
S tronic Link
Further indicator lamps

Turn signals
Link

Trailer turn signals*
Link

Cruise control system*
Link

Adaptive cruise control*
Link

Adaptive cruise control*
Link

Hold assist*
Link

Active lane assist*
Link

Start/stop system*
Link

Start/stop system*
Link

Rest recommendation*
Link

Main beam assist*
Link

Main beam headlights
Link, Link

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