Mercedes 203 C-class represents the second generation of the model range which was produced in 2000, 2001, 2002, 2003, 2004, 2005, 2006 and 2007 with w203 sedan, s203 station wagon, coupe (C160, C180, C230, C240, C280, C320). During this time, the model has been restyled. In this publication you will find information on the location of electronic control units, a detailed description of the fuses and relays Mercedes 203 with box diagrams and photo examples of their location. Note the fuses responsible for the cigarette lighter and fuel pump.
The location of the blocks and the design of the elements in them may differ from the one shown and depends on the year of manufacture, the region of delivery and the level of electrical equipment of your car.
Contents
Location
Layout
Assignment
| 1 | Air conditioner/heater control unit – in the heater control panel |
| 2 | A/C/Heater Fan Control Module – Next to the fan motor |
| 3 | Air purity sensor (air conditioning system) |
| 4 | Sunlight sensor (air conditioning system) |
| 5 | Antenna signal booster – 1, rear window top |
| 7 | Anti-theft control unit (integrated with the multifunctional control unit) – left side of the luggage compartment |
| 8 | Vehicle inclination sensor (anti-theft system) – left side of the luggage compartment |
| 9 | Anti-theft horn – Behind wheel arch trim |
| 10 | Volume change sensors (anti-theft system) |
| 11 | Audio unit – in navigation system |
| 12 | Audio output amplifier (if equipped) – right side of luggage compartment |
| 13 | Additional heater control unit |
| 14 | Auxiliary Heater Remote Control Receiver – Under Dashboard (Rear Luggage Compartment) |
| 15 | Accumulator battery |
| 16 | Brake booster vacuum pump control unit |
| 17 | Central locking signal sensor (infrared) – in the handle of the driver’s door |
| 18 | Diagnostic connector (DLC) |
| 19 | Driver’s door electrical control unit |
| 20 | Left rear door electrical control unit |
| 21 | Passenger door electrical control unit |
| 22 | Control unit for electrical equipment of the right rear door |
| 23 | Fuse/Relay Box, Engine Compartment 1 |
| 24 | Fuse box/relay dashboard |
| 25 | Fuse/Relay Box, Luggage Compartment |
| 26 | Headlight control unit, left (models with xenon headlights) |
| 27 | Headlight control unit, right (models with xenon headlights) |
| 28 | Sound signals 1/2 – behind the grille |
| 29 | Ignition lock control unit |
| 30 | Electronic immobilizer control unit – (integrated with ignition lock control unit) |
| 31 | Turn signal/alarm relay – in multifunction control box 2 |
| 32 | Lighting control unit – behind the headlight switch |
| 34 | Multifunction Control Module 1 – Attached to Engine Compartment Fuse/Relay Box – Functions: Interior Lamps, Headlights, Horns, Windshield Wipers, A/C Pressure Control, Headlight Washers, Coolant Level, Brake Fluid Level, Thermometer, Power Actuator door mirrors |
| 35 | Multifunction control unit 2 – connected by fuse / relay box, luggage compartment – functions: Central locking, fuel level, anti-theft system, alarm, rear window defroster, taillights, trunk lid opener, rear window wiper (wagon) |
| 36 | Navigation system control unit |
| 37 | Ambient temperature sensor |
| 38 | Parking system control unit – under the panel, in the rear of the luggage compartment |
| 39 | Rain sensor – upper center windshield |
| 40 | Power seat control unit (with memory), front left – under the seat |
| 41 | Power seat control unit (with memory), front right – under the seat |
| 42 | Seat heating control unit, front – in the switch block |
| 43 | Electronic transmission control unit – sequential manual transmission |
| 44 | Side impact sensor, left – under the rear seat |
| 45 | Side impact sensor, right – under the rear seat |
| 46 | SRS electronic control unit |
| 47 | Steering column electrical control unit – behind the steering wheel |
| 48 | Steering column lock control unit – built into the ignition lock control unit |
| 49 | Sunroof electric control unit |
| 50 | Body height sensor, front (models with xenon headlights) – front anti-roll bar |
| 51 | Body height sensor, rear (models with xenon headlights) – rear axle |
| 52 | Telephone network connection module – under the panel, in the rear of the luggage compartment |
| 53 | Telephone interface control unit – under the panel, in the rear of the luggage compartment |
| 54 | Phone transceiver – under the panel, in the rear of the luggage compartment |
| 55 | Trailer electrical control unit – under the panel, in the rear of the luggage compartment |
| 56 | Electronic gearbox control unit |
| 57 | Shift control unit – automatic transmission selector |
| 59 | Voice activation system unit – under the panel, in the rear of the luggage compartment |
| 60 | Fuse/Relay Box, Engine Compartment 2 |
The location of the fuse and relay boxes in the Mercedes w203
Designation
- F32 – Power fuse box
- F34 – Fuse box in the instrument panel
- N10/1 – Fuse and relay box in the engine compartment
- N10/2 – Fuse box and relay luggage compartment
Passenger compartment
In the cabin, the fuse box is located on the left side of the dashboard behind a protective cover.
Diagram
Allocation
| 21 | 30A Left front door control unit |
| 22 | 30A Right front door control unit |
| 23 | 15A Cigarette lighter |
| 24 | 7.5A CD player with changer (in glove compartment) |
| 25 | 30A Upper control panel control unit |
| 26 | 25A Audio Amplifier |
| 27 | 30A Driver’s seat power adjustment control unit (with memory) |
| 28 | 30A Spare fuse |
| 29 | 30A Driver’s seat power adjustment control unit (with memory) |
| Multifunctional control unit (taxi) | |
| 30 | 40A Heater air circulation unit |
| 31 | 20A EIS control unit |
| Ignition lock control unit | |
| 32 | 30A Left rear door control unit |
| 33 | 30A Right rear door control unit |
| 34 | 7.5A Terminal 30 socket |
| Until 31.5.01: | |
| Cell phone and D2B transceiver (for built-in phone) | |
| Cell phone and transceiver TELE AID D2B (for built-in phone) | |
| Phone interface (for optional cell phone) | |
| CTEL compensator (for additional cell phone) | |
| 15A Before 31.3.04: Power passenger seat adjustment control unit (with memory) | |
| Until 31.5.03, Taxi: Multifunctional control unit | |
| From 1.6.03, Taxi: Multifunction control unit | |
| From 1.6.01, Police: Multifunction control unit | |
| 30A From 1.4.04: Passenger seat power adjustment control unit (with memory) | |
| From 1.4.04, Taxi: Multifunction control unit | |
| 35 | 30A Until 31.3.04: STH heater unit |
| 20A From 1.4.04: STH heater unit | |
| 36 | 30A Before 31.3.04, Police: Additional equipment power connector |
| 15A Engines 612.990 (up to 29.2.04): Charge air cooler circulation pump | |
| From 1.4.04, Japan: Audio interface control unit | |
| 7.5A Universal mobile phone interface | |
| 37 | 25A Air cooler circulation pump |
| Up to 29.2.04: Brake booster vacuum pump control unit | |
| 38 | 30A Up to 29.2.04: Power passenger seat adjustment control unit (with memory) |
| From 1.4.04, Police: Multifunction control unit | |
| 39 | 30A Spare fuse |
| 40 | 7.5A Passenger seat power adjustment control unit (with memory) |
| Universal mobile phone interface | |
| cell phone separation point | |
| Telephone interface | |
| Radiotelephone network compensator E | |
| From 1.6.01, MB phone: Cell phone and transceiver | |
| From 1.6.01, TELE AID: Cell phone and transceiver | |
| From 1.4.04, Japan: E-call control unit | |
| 30A Up to 31.5.01: Multifunction control unit | |
| 41 | 7.5A Upper control panel control unit |
| Up to 31.5.01: KLA system control panel (Automatic climate control system) | |
| 15A From 1.6.01: KLA system control panel (Automatic climate control system) | |
| 42 | 7.5A Instrument cluster |
In the Mercedes 203, fuse 23 is responsible for the cigarette lighter. Another fuse is located in the block under the hood or luggage compartment (USA).
Engine compartment
Main fuse and relay box
Under the hood in the engine compartment on the left side under the protective cover is the fuse and relay box (N10/1).
Diagram
Appointment
| 43a | 15A Horn relay |
| 43b | 15A Horn relay |
| 44 | 5A D2B interface |
| Telephone interface | |
| Connector ferrule 15R | |
| TELE AID control unit | |
| 45 | 7.5A SRS control unit |
| 46 | 40A Wiper On/Off Relay |
| Wiper Mode Relay 1/2 | |
| 47 | 15A Glove box lights with sensor-switch |
| Front cigarette lighter (illuminated) | |
| 48 | 15A Engines 612.990 (up to 31.3.04): Brake booster vacuum pump control unit |
| Motors 112, 113: Fuse-protected connector sleeve 15 | |
| Engines 646, USA (up to 31.3.04): Fused connector sleeve 30 | |
| Engines 646 (from 1.4.04): O2 probe before catalytic converter | |
| 49 | 7.5A SRS control unit |
| 50 | 5A Light switch module |
| Engines 612.990 | |
| Preheating output stage (until 31.3.04) | |
| Mass Air Flow Sensor (1.4.04 to 30.11.04) | |
| 51 | 7.5A AAC (automatic A/C) with built-in auxiliary fan electric motor |
| instrument cluster | |
| For AAS “comfort”: | |
| AAC failure sensor | |
| Solar radiation sensor AAC (4 pieces) | |
| For all vehicles with xenon headlights: | |
| Left block headlight | |
| Right block headlight | |
| AMG: Charge air cooler circulation pump | |
| 203.0 (until 31.7.01): SRS control unit | |
| 52 | 15A Starter |
| 53 | 25A Diesel engines: |
| Starter relay | |
| Rear SAM control box with relay and fuse box | |
| Engines 611/612/642/646: CDI control unit | |
| 15A Gasoline engines: | |
| Starter relay | |
| Rear SAM control box with relay and fuse box | |
| Engines 111/271/272: ME control unit | |
| Engines 112/113: | |
| ME control unit | |
| Cable termination electr. circuit terminal 87 M1e | |
| 54 | 15A Engines 271.940: |
| ME control unit | |
| Vent valve (USA) | |
| Canister shut-off valve | |
| Engines 271.942: NOX control unit | |
| Engines 642/646: CDI control unit | |
| Motors 642/646: Cable termination electr. terminal 30 circuits | |
| 7.5A Engines 611/612: CDI control unit | |
| Engines 611/612 (until 11/30/04): Heating element in the ventilation duct | |
| 55 | 7.5A Steering wheel sensor |
| Distronic: DTR control unit | |
| Gearbox 722: | |
| ETC control unit [EGS] (up to 31.5.04) | |
| Selector lever electronic control unit | |
| VGS control unit | |
| Gearbox 716: | |
| Sequentronic control unit | |
| Transmission Position Sensor | |
| 56 | 5A ESP and BAS control unit |
| Brake light switch | |
| 57 | 5A Steering wheel sensor (up to 31.5.02) |
| Electronic ignition control unit / sensor-switch opening the starter circuit | |
| Steering column electronic module (as of 1.6.02) | |
| Engines 112/113: ME control unit | |
| 58 | 40A Transmission 716: Hydraulic pump |
| 59 | 50A ESP and BAS control unit |
| 60 | 40A ESP and BAS control unit |
| 61 | 15A Transmission 716: Sequentronic control unit |
| 62 | 5A Diagnostic connector |
| Lighting control module | |
| Brake light switch | |
| 63 | 5A Lighting control module |
| 64 | 10A Radio receiver |
| Radio and navigation | |
| Display and function control unit COMAND | |
| 65 | 40A Engines 112/113: Electric air pump |
| Relay | |
| I | Horn relay |
| K | Terminal 87 relay, chassis |
| L | Wiper Mode Relay 1/2 |
| M | Relay terminal 15R |
| N | KSG pump control relay |
| O | Air Pump Relay (Engines 112, 113, 271) |
| P | Relay terminal 15 |
| Q | Relay on/off wiper |
| R | Terminal 87 relay, motor |
| S | Starter relay |
Power fuse box
An additional high power fuse box in the form of fuse links is installed next to the battery.
Photo example
Diagram
Decoding
- 125A Fuse box in the instrument panel
- 200A SAM control unit, rear
- 125A Additional fuse box
- 200A SAM control unit, front
- 125A Electric suction fan for engine and air conditioner with integrated regulator Diesel engines: Preheat output stage
- 60A SAM control unit, front
Luggage compartment
It is located in the luggage compartment behind the trim.
Diagram
Assignment
| 1 | 30A Front right seat adjustment switch box |
| Switch for partially electric adjustment of the front passenger seat | |
| 2 | 30A Front left seat adjustment switch box |
| Driver’s seat partially electric adjustment switch | |
| 3 | 7.5A Interior lighting |
| trunk lighting | |
| Remote control receiver | |
| Tire inflation pressure control | |
| 20A TV tuner | |
| 4 | 20A Fuel pump relay |
| 5 | 20A Engines 112.961 (up to 31.3.04): Charge air cooler circulation pump |
| Except 112.961: Reserve relay 2 | |
| 6 | 25A Spare fuse |
| 7 | 7.5A Backup relay 1 |
| 8 | 7.5A Rear window aerial amplifier module |
| Alarm siren | |
| ATA tilt sensor | |
| 9 | 25A Overhead control panel control box |
| 10 | 40A Rear window defroster |
| 11 | 20A Spare fuse |
| 12 | 15A Accessory Power Connector |
| 203.0 – USA (until 31.3.04): Rosette | |
| 13 | 5A Air pump for multi-contour seat |
| Voice Control System (VCS) – Voice Control Unit | |
| Cell phone Motorola Star TAC, retrofit – D2B interface for portable mobile phone | |
| Rear Reading Light | |
| Signal display PTS (Parktronic) | |
| PTS control unit (parktronic) | |
| 14 | 15A Rear stack wiper |
| 15 | 10A Filler relay, polarity receiver |
| 16 | 20A For VSC: Voice control box |
| For CTEL Motorola Star TAC, retrofit: D2B interface for mobile phone | |
| 17 | 20A Trailer control unit |
| 18 | 20A Drawbar socket, 13-pin |
| 19 | 20A Air pump for multi-contour seat |
| 20 | 15A Rear window dimming |
| 203.2/7 – USA: Rosette | |
| Relay | |
| A | Fuel pump relay |
| B | Relay 2, terminal 15R |
| C | Backup relay 2 |
| D | Backup relay 1 |
| E | Rear defroster relay |
| F | Relay 1, terminal 15R |
| G | Filler relay, polarity switch 1 |
| H | Filler relay, polarity switch 2 |
There is something to supplement this post – write in the comments.
have a 2006 c230 MBZ Instrument Cluster will not go a sleep at night – odomoter window
stays illuminated and drains battery…tried changing the cluster to a used one….it worked
did the reset with all….Light went off….all good….then in the evening …the light appeared again (the odometer box only-the 2 boxes in the middle of cluster ??) so it did it again- Is there a relay for the Accessory delay RELAY? a speedo guy said to change that out ?
back up relay 2 an 1, or C an D, what are they used for
I have a mercedes C220 2006
My expartner removed the starter relay (con trick for blackmail).
Not knowing I tried to tow it to a safer place it was left on a school crossing.
I tried to un lock with fob new batteries by main dealer.
No response head lights on ,radiator fan on all the time. It’s a crying shame. Iv got NO WORKING KIDNEYS HAEMODIALYSIS PATIENT LITTLE MONEY
I BOUGHT IT FOR THE WIFE SHE DIED ON 17 NOVEMBER 2022 I WAS DEVISTATED.
that’s very helpful
Fiited a new engin Sam box, in mercedes c180 2002, car still doesn’t want to start need help to diagnose the problem starter swing perfectly when by passed from battery direct to starter.
My c220 2003 parking lights do not turn off after locking the car please any help
The M position in the front SAM panel is labeled as M15 and is a relay. The wired connector is plugged in from the top and has 5 wires going to it. They are as follows, grey wire w/purple stripe, brown w/yellow stripe, red w/stripe, blue w/red stripe, and a heavier gauged wire that is red w/yellow stripe. The red yellow wire is in the loom but splits off and goes downward in front of the SAM box but can’t seem to see where it goes yet. The other four comes out of the box and heads towards the front of the car with the wires dangling not conectes to anything. I don’t see any other place where it may have come from. I’ve done extensive research online but I guess I’m not looking in the right places. This is the first chat room that even came close to what I was talking about. If anyone is familiar with anything mentioned here please share anything that might help me get to the next level of figuring this out. Thanks!