Mercedes-Benz B-Class (2012 – 2018) Fuse Box Location & Diagrams
The Mercedes-Benz B-Class (2012-2018) is known for its comfort and performance, but understanding its electrical system is key to maintaining that quality. In this guide, we’ll walk you through the fuse box diagrams and locations for this model range, helping you identify the right fuse and replace it with ease. Whether you’re troubleshooting an electrical issue or performing regular maintenance, this guide is a must-have for all B-Class owners.
Passenger Compartment Fuse Box
Mercedes-Benz B-Class (2012 to 2018)
Fuse box location
The fuse box is located under the floor near the passenger seat.
- Fold out perforated floor covering (1) in the direction of the arrow.
- To release cover (3), press retaining clamp (2).
- Fold-out cover (3) in the direction of the arrow to the catch.
- Remove cover (3) forwards.
- Fuse allocation chart (4) is located on the lower right-hand side of the cover (3).
Fuse box diagram
| No | Fused function | Amp |
|---|---|---|
| 21 | Valid for diesel engine: PTC heater booster | 150 |
| 22 | Additional battery relay for ECO start/stop function | 200 |
| 23 | Left front door control unit | 30 |
| 24 | Right front door control unit | 30 |
| 25 | SAM control unit | 30 |
| 26 | ECO start/stop additional battery connector sleeve | 10 |
| 27 | Engine compartment fuse and relay module | 30 |
| 28 | Vehicle interior sound generator control unit Electric Drive (W242): Thermal management control unit | 5 |
| 29 | up to 02.11.2014: Trailer socket as of 03.11.2014: Trailer recognition control unit | 15 |
| 30 | Trailer recognition control unit | 5 |
| 31 | 4MATIC: All-wheel drive control unit | 5 |
| 32 | Steering column tube module control unit | 5 |
| 33 | Audio/COMAND control panel | 5 |
| 34 | ACC control and operating unit | 7,5 |
| 35 | Rear window heater | 40 |
| 36 | Driver seat control unit Driver seat lumbar support adjustment control unit | 7,5 |
| 37 | Audio/COMAND display | 7,5 |
| 38 | Supplemental Restraint System control unit | 7,5 |
| 39 | Overhead control panel control unit | 10 |
| 40 | Valid for engine 651 (Emissions standard EU6): Powertrain control unit | 15 |
| 40 | Electric Drive (W242): Powertrain control unit | 5 |
| 41 | Panoramic sliding sunroof control module | 30 |
| 42 | Radio (Audio 5 USB, Audio 20 CD, Audio 20 CD with CD changer) COMAND controller unit | 5 |
| 42 | Radio (Radio 20, Audio 20 USB) | 25 |
| 43 | Parking system control unit | 5 |
| 44 | Left front reversible emergency tensioning retractor | 40 |
| 45 | Right front reversible emergency tensioning retractor | 40 |
| 46 | Front passenger seat control unit Front passenger seat lumbar support adjustment control unit | 7,5 |
| 47 | Navigation module | 7,5 |
| 47 | Adaptive damping system control unit | 25 |
| 48 | Spare | – |
| 49 | Control unit for Drive Kit for iPhone® | 7,5 |
| 49 | COMAND fan motor | 5 |
| 50 | Spare | – |
| 51 | Spare | – |
| 52 | Electric Drive (W242): Park pawl actuator motor | 30 |
| 53 | Spare | – |
| 54 | Spare | – |
| 55 | Telematics services communications module KEYLESS-GO control unit | 5 |
| 56 | Steering column tube module control unit | 10 |
| 57 | Lane Keeping Assist: Special-purpose vehicle multifunction control unit | 30 |
| 57 | Special vehicle: Special-purpose vehicle multifunction control unit | 7.5 |
| 57 | Electric Drive (W242): Park pawl actuator motor circuit 87 relay (F34kG) | 5 |
| 58 | Emergency vehicle fuse box | 30 |
| 59 | Front passenger seat control uni | 30 |
| 60 | Driver seat control unit | 30 |
| 61 | Sound system amplifier control unit | 40 |
| 62 | Valid for transmission 711: Electric steering lock control unit | 20 |
| 63 | Fuel system control unit | 25 |
| 63 | Electric Drive (W242): Gateway powertrain control unit | 5 |
| 64 | Electronic Toll Collection control unit Dedicated Short-Range Communications control unit | 1 |
| 65 | Glove compartment lamp | 5 |
| 66 | Emergency vehicle fuse box | 15 |
| 66 | Special-purpose vehicle interface | 5 |
| 67 | Spare | – |
| 68 | Spare | – |
| 69 | Spare | – |
| 70 | Rear center console socket | 25 |
| 71 | Luggage compartment socket | 25 |
| 72 | Front cigarette lighter with ashtray illumination Vehicle interior power outlet | 25 |
| 73 | Electric parking brake control unit | 30 |
| 74 | Electric parking brake control unit | 30 |
| 75 | Trailer recognition control unit | 20 |
| 75 | Electric Drive (W242): Battery management system control unit (N82/2) | 5 |
| 76 | Trailer recognition control unit (N28/1) | 25 |
| 76 | Electric Drive (W242): Park pawl control unit | 5 |
| 77 | Trailer recognition control unit | 25 |
| 78 | Emergency vehicle fuse box | 40 |
| 79 | SAM control unit | 40 |
| 80 | SAM control unit | 40 |
| 81 | Blower regulator | 40 |
| 82 | Overhead control panel control unit | 10 |
| 83 | Electronic ignition lock control unit | 7,5 |
| 84 | Upper control panel control unit | 5 |
| 85 | ATA [EDW]/tow-away protection/interior protection control unit | 5 |
| 86 | FM, AM and CL [ZV] antenna amplifier as of 01.06.2016: Cellular telephone system antenna amplifier / compensator | 5 |
| 87 | Diagnostic connector | 10 |
| 88 | Instrument cluster | 10 |
| 89 | Exterior lights switch | 5 |
| 90 | Left rear bumper intelligent radar sensor Intelligent radar sensor for right rear bumper | 5 |
| 91 | Pedal operation monitor switch Footwell illumination switch Electric Drive (W242): Battery management system control unit | 5 |
| 92 | Fuel system control unit Electric Drive (W242): Gateway powertrain control unit | 5 |
| 93 | Electric parking brake control unit | 5 |
| 94 | Supplemental Restraint System control unit | 7,5 |
| 95 | Front passenger seat occupied recognition and ACSR Weight sensing system (WSS) control unit | 7,5 |
| 96 | Tailgate wiper motor | 15 |
| 97 | Mobile phone electrical connector | 5 |
| 98 | SAM control unit | 5 |
| 99 | Tire pressure monitor control unit | 5 |
| 100 | Valid for engine 133: DIRECT SELECT INTERFACE | 5 |
| 101 | 4MATIC: All-wheel drive control unit | 10 |
| 102 | Stationary heater radio remote control receiver Electric Drive (W242): Powertrain control unit Valid for AMG vehicles as of 01.09.2015: Transmission mode control unit as of 01.06.2016: Antenna changeover switch for telephone and stationary heater | 5 |
| 103 | Emergency call system control unit Telematics services communications module HERMES control unit | 5 |
| 104 | Media interface control unit Multimedia connection unit | 5 |
| 105 | Digital Audio Broadcasting control unit Satellite digital audio radio (SDAR) control unit | 5 |
| 105 | Tuner unit | 7,5 |
| 106 | Multifunction camera | 5 |
| 107 | Digital TV tuner | 5 |
| 108 | up to 31.05.2016: Reversing camera | 5 |
| 108 | as of 01.06.2016: Reversing camera | 7,5 |
| 109 | Charging socket electrical connector | 20 |
| 110 | Radio COMAND controller unit Engine sound control unit | 30 |
| Relay | ||
| A | Circuit 15 relay | |
| B | Rear window wiper relay | |
| C | Circuit 15R2 relay | |
| D | Heated rear window relay | |
| E | Circuit 15R1 relay | |
| F | Circuit 30g relay | |
| G | Electric Drive (W242): Park pawl actuator motor circuit 87 relay |
Front Electrical Prefuse Box
Mercedes-Benz B-Class (2012 to 2018)
Fuse Box Location
Fuse Box Diagram
| No | Fused function | Amp |
|---|---|---|
| 1 | Alternator | 300 |
| 1 | Electric Drive (W242): DC/DC converter control unit | 400 |
| 2 | Vehicle interior fuse box | 200(petrol) 250(diesel) |
| 3 | Electrical power steering control unit | 100 |
| 4 | SAM control unit | 40 |
| 5 | Fan motor | 80 |
| 6 | Valid for engine 607: Fuel preheating control unit | 70 |
| 7 | Valid for engine 607 (Emissions standard EU5): DPF regeneration heater booster control unit | 125 |
| 8 | Valid for engine 607, 651: Glow output stage | 100 |
| Relay | ||
| F32kl | Decoupling relay |
Engine Compartment Fuse Box
Mercedes-Benz B-Class (2012 to 2018)
Fuse box location
Fuse box diagram
| No | Fused function | Amp |
|---|---|---|
| 201 | Alarm siren | 5 |
| 202 | Stationary heater control unit | 20 |
| 202 | Electric Drive (W242): Park pawl control unit circuit 87 relay | 5 |
| 203 | LED headlamp: Right front lamp unit | 15 |
| 203 | Electric Drive (W242): Powertrain control unit | 5 |
| 204 | Electronic Stability Program control unit | 25 |
| 205 | Left fanfare horn Right fanfare horn | 15 |
| 206 | Valid for engine 651: CDI control unit Valid for engine 607: Powertrain control unit Electric Drive (W242): Brake booster vacuum pump relay Circuit relay 87M | 5 |
| 207 | Valid for diesel engine: Circuit relay 87M Electric Drive (W242): High-voltage battery cooling shutoff valve Park pawl control unit | 5 |
| 208 | Valid for engine 133, 607: Circuit 87 relay | 7.5 |
| 208 | Electric Drive (W242): Fan motor | 5 |
| 209 | LED headlamp: Left front lamp unit | 15 |
| 209 | Electric Drive (W242): Spare | – |
| 210 | Heated windshield relay | 5 |
| 210 | as of 03.11.2014 except (Canada version): Starter front-end relay | 5 |
| 211 | Natural Gas Drive (W242): CNG control unit | 7.5 |
| 211 | Electric Drive (W242): Heater circuit circulation pump | 15 |
| 212 | Valid for engine 133, 270: Connector sleeve, circuit 87M3 Valid for engine 651: Valid for engine 607 (Emissions standard EU5): Valid for engine 607 (Emissions standard EU6): Oxygen sensor upstream of catalytic converter Valid for engine 607: CDI control unit Electric Drive (W242): Electric drive and charger coolant pump | 15 |
| 213 | Valid for engine 133, 270, 651: Connector sleeve, circuit 87 M2e Valid for engine 607 (Emissions standard EU5): Valid for engine 607 (Emissions standard EU6): Electric Drive (W242): Battery cooling system coolant pump 1 | 15 |
| 214 | Valid for engine 133, 270, 651: Connector sleeve, circuit 87 M4e | 10 |
| 214 | Electric Drive (W242): Battery cooling system coolant pump 2 | 15 |
| 215 | Valid for gasoline engine: Cylinder 1 ignition coil Cylinder 2 ignition coil Cylinder 3 ignition coil Cylinder 4 ignition coilValid for engine 651: Quantity control valveValid for engine 607: CDI control unit Boost pressure positioner Quantity control valve | 20 |
| 215 | Electric Drive (W242): Thermal management control unit Gateway powertrain control unitElectric Drive (W242) as of 03.11.2014: High-voltage power distributor | 5 |
| 216 | Valid for gasoline engine: ME-SFI control unit Valid for engine 607: Powertrain control unit | 5 |
| 217 | Valid with transmission 724: Dual clutch transmission fully integrated transmission control unit | 25 |
| 218 | Electronic Stability Program control unit | 5 |
| 219 | Electric Drive (W242): Park pawl control unit | 5 |
| 220 | Transmission cooling coolant circulation pump | 10 |
| 221 | Electric Drive (W242): Vacuum pump | 40 |
| 222 | Electric Drive (W242): Electrical refrigerant compressor | 7.5 |
| 223 | Spare | – |
| 224 | DISTRONIC electric controller unit COLLISION PREVENTION ASSIST controller unit | 7.5 |
| 225 | Electric Drive (W242): Powertrain control unit | 5 |
| 226 | Natural Gas Drive (W242): CNG control unit Electric Drive (W242): Charger control unit Power electronics control unit | 5 |
| 227 | Electric Drive (W242): Power electronics control unit | 5 |
| 228 | Electric Drive (W242): Electric vehicle sound generator | 5 |
| 229 | Left front lamp unit | 5 |
| 230 | Electronic Stability Program control unit | 5 |
| 231 | Right front lamp unit | 5 |
| 232 | Headlamp control unit | 15 |
| 233 | Spare | – |
| 234 | Valid for engine 607: Powertrain control unit | 5 |
| 234 | Electric Drive (W242): High-voltage power distributor | 10 |
| 235 | Valid for engine 607: Fan motor, Radiator shutters actuator | 7.5 |
| 235 | Valid for engine 133: Charge air cooler circulation pump, Charge air cooler circulation pump | 7.5 |
| 236 | SAM control unit | 40 |
| 237 | Electronic Stability Program control unit | 40 |
| 238 | Heated windshield | 50 |
| 239 | Wiper speed 1/2 relay | 30 |
| 240A | Starter circuit 50 relay | 25 |
| 240A | Electric Drive (W242): Powertrain control unit | 7.5 |
| 240B | Circuit 15 relay (not latched) | 25 |
| 241 | Electric Drive (W242): High-voltage PTC heater | 7.5 |
| Relay | ||
| J | Fanfare horn relay | |
| K | Wiper speed 1/2 relay | |
| L | Windshield wiper ON/OFF relay | |
| M | Starter circuit 50 relay Electric Drive (W242): Circuit 87C relay | |
| N | Circuit relay87M | |
| 0 | ECO start/stop: Transmission cooling coolant circulation pump relay Electric Drive (W242): Park pawl control unit circuit 87 relay | |
| P | Backup relay (F58kP) | |
| Q | Circuit 15 relay (not latched) Electric Drive (W242): Brake booster vacuum pump supply relay (F58kQ) | |
| R | Circuit 15 relay | |
| S | Circuit 87 relay | |
| T | Heated windshield relay |
