Audi A4 S4 B9 (2016 – 2023) fuse and relay

The Audi A4 B9 was produced in 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023 and 2024 with the designations B9 and 8W. During this time, the model underwent restyling. In this article you can find a description of the fuses and relays of the Audi A4 S4 B9 with diagrams, their locations and photo examples of execution. Let’s highlight the fuse responsible for the cigarette lighter.

Audi A4 B9

The purpose of fuses and relays may differ from those presented and depend on the year of manufacture, the level of electrical equipment and the region of delivery of your Audi A4 B9.

Passenger compartment

Fuse and relay box

Inside the car, the fuse and relay box is located on the left side, under the instrument panel.

Left-hand drive vehicles




Right-hand drive vehicles

location RHD


Diagram 1


Panel A (brown)
1Catalytic converter heating
2Engine components
3Exhaust doors, fuel injectors, air intake, engine heating
4Vacuum pump, hot water pump, NOx sensor, particulate matter sensor, biodiesel sensor, exhaust doors
5Brake light sensor
6Engine valves, camshaft adjustment
7Heated oxygen sensors, mass air flow sensor, water pump
8Water pump, high pressure pump, high pressure regulator valve, temperature valve, engine mount
9Hot water pump, engine relay, 48V starter-alternator, 48V water pump
10Oil pressure sensor, oil temperature sensor
11Clutch Position Sensor, 48V Starter Alternator, Water Pump, 12V Starter Alternator
12Engine valves, engine mount
13Engine cooling
14Fuel injectors, drive system control module
15Ignition coils, heated oxygen sensors
16Fuel pump


Panel B (red)
1Anti-theft system
2Drive System Control Module
3Front left seat electronics, lumbar support, massage seat
4Automatic transmission selector lever
6Parking brake
7Diagnostic interface (gateway control module)
8Roof electronics control module
9Emergency call and communication control module
10Airbag control module
11Electronic Stability Control (ESC), Anti-lock Braking System (ABS)
12Diagnostic connector, light/rain sensor
13Climate control system
14Right front door control unit
15Climate control compressor
16Brake system reservoir


Panel C (black)
1Heated front seats
3Left headlight electronics
4Panoramic glass roof/ sliding/ tilting sunroof
5Left front door control unit
612 volt socket, cigarette lighter
7Right rear door control unit, right rear window regulator
8All Wheel Drive (AWD) Control Module
9Right headlight electronics
10Windshield washer/headlight washer control module
11Left rear door control module, left rear power window
12Autonomous heater

Fuse number 6 is responsible for the operation of the cigarette lighter.

Panel D (black)
1Front seat electronics, seat ventilation, rear view mirror, rear climate control system control panel, heated windshield, diagnostic connector
2Diagnostic interface, on-board network control module
3Sound generator
4Clutch position sensor
5Engine start, emergency shutdown
6Diagnostic connector, traffic information aerial (TMC)
7USB connection
8Garage door opener
9Audi Adaptive Cruise Control, Adaptive Distance Control
11Front camera
12Right headlight
13Left headlight
14Transmission Fluid Cooler / Rear Window Wiper
15Alarm and hands-free calling system

Panel E (red)
1Ignition coils
2Climate control compressor
5Left headlight
6Automatic transmission
8Climate control fan
9Right headlight
10Dynamic Steering
11Engine starting

Fuse box

There is another fuse box installed at the left end of the dashboard on the left side.

location 2


Diagram 2


  1. Convenient access and launch authorization control module (NFC)
  2. Audi phone, USB connector
  3. Head-up display
  4. Audi music interface, USB connection
  5. Front climate control panel
  6. Steering column lock
  7. Central display
  8. Instrument panel
  9. Volume control, Infotainment unit
  10. Light switch, switch module
  11. Steering column electronics
  12. Particulate matter sensor for climate control system
  13. Infotainment system
  14. Heated steering wheel, Electronic steering column

Luggage compartment

This fuse box is located in the luggage compartment on the left side, behind the trim.

location 3


Diagram 3


Panel A (black)
2Heated windshield
3Heated windshield
5Suspension control
6Automatic transmission
7Heated rear window
8Rear seat heating
9Left rear lights
10Airbag, driver’s side seat belt pretensioner control module
11Trunk lid lock, fuel filler flap lock, comfort system control unit
12Luggage compartment lid
Panel B (red)
6Battery Power Interruption / Electric Compressor
Panel C (brown)
1External antenna
2Audi phone booth
3Right front seat electronics, lumbar support, massage seat
4Lateral assistance
6Tire pressure monitoring system
7Convenient access and launch authorization control module (NFC)
8Additional heating, tank module
10TV tuner, data exchange and telematics control module
11Auxiliary Battery Control Module
12Garage door opener
13Rear view camera, peripheral cameras
14Right rear lights
16Airbag, front passenger seat belt tensioner control module
Panel E (red)
3Exhaust treatment (Adblue)
5Right trailer light
7Trailer hitch
8Left trailer light
9Trailer socket
10All Wheel Drive Control Module, Sport Differential
11Exhaust treatment (Adblue)

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Comments 1

  • Hi, my 2020 RHD S4 fuse box in the passenger footwell bears no relation – I can send you a photo. I need to identify which fuse to pull to isolate a function, but it’s not as per your page here.

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