Understanding your 2003 Ford Excursion’s electrical system is crucial for maintenance and troubleshooting. A key component of this system is the fuse box, which protects your vehicle’s circuits from overloads. Alongside the fuse box, the OBD2 port is vital for diagnostics, allowing you to read trouble codes and understand your vehicle’s health. This guide provides a detailed look at the fuse box diagram for the 2003-2006 Ford Expedition, which shares similarities with the 2003 Excursion, and how it relates to your vehicle’s OBD2 system.
Knowing the location and function of each fuse can save you time and money when dealing with electrical issues. Whether you’re experiencing problems with your lights, wipers, or even suspect issues affecting your OBD2 readings, this information is your starting point.
Locating the Power Distribution Box in Your 2003 Ford Excursion
The primary fuse box, also known as the power distribution box or passenger compartment fuse panel, in your 2003 Ford Excursion is located inside the vehicle. You’ll find it conveniently placed under the right-hand side of the instrument panel, making it accessible from the passenger side.
Passenger Compartment Fuse Box Diagram for 2003 Ford Expedition, highlighting the location relevant to diagnosing electrical systems and potential OBD2 related issues.
2003-2006 Ford Expedition Fuse Box Diagram and Fuse Functions
Below is a detailed table outlining the fuses and relays within the passenger compartment fuse box for the 2003-2006 Ford Expedition. While this diagram is specifically for the Expedition, the general layout and many of the functions are applicable to the 2003 Ford Excursion, especially regarding common systems monitored by OBD2.
| № | A | Description |
|---|---|---|
| 1 | 7.5 | Run/Accessory – Front wiper motor, Instrument cluster, Rear wiper motor |
| 2 | 20 | Turn signal/Hazard flasher, Stoplamp switch, Stoplamps, Center high-mount stop light (CHMSL), Turn signal lamps |
| 3 | 7.5 | Power mirror switch, Power mirrors (non-memory), Driver seat switch (memory), Memory module (logic power) |
| 4 | 15 | DVD player, Rear seat audio controls, CDDJ (navigation radio) |
| 5 | 7.5 | Powertrain Control Module (PCM) (KA power), Speed control deactivation switch, Manual climate control mode switch, Stoplamp switch, Brake-shift interlock (BSI) solenoid, EATC control head, Body Security Module (BSM) (KA power), 3rd row seat relay coils, SecuriLock LED |
| 6 | 15 | Headlamp switch (parklamps and switch backlight feed), Parklamps, License plate lamps, Foglamp relay coil, Trailer tow electric brake controller (illumination), BSM (autolamp, parklamps) Foglamp indicator |
| 7 | 5 | Radio (start signal) |
| 8 | 10 | Rear window defroster switch, Rear window defroster indicator (climate control head), Heated outside mirrors |
| 9 | – | Not used |
| 10 | 20 | Trailer tow back-up lamps relay, Trailer tow 7–wire connector (back-up lamps), Trailer tow parklamp relay, Trailer tow 7– and 4–pin connectors (parklamps) |
| 11 | 10 | A/C compressor clutch relay, A/C compressor clutch solenoid, 4×4 Integrated Wheel Ends (IWE) solenoid |
| 12 | 15 | Fuel pump relay, Fuel pump shut-off switch, Fuel pump driver module, Fuel pump motor |
| 13 | 10 | Manual climate control mode switch, Rear window defroster relay coil, A/C refrigerant containment switch, A/C de-icing switch, A/C low pressure switch, DATC control head, DATC solenoids, DATC blower control, Trailer tow battery charge relay coil |
| 14 | 10 | Daytime Running Lamps (DRL) ignition relay coil, Digital Transmission Range Sensor (DTRS) back-up lamps, Trailer tow back-up lamps relay coil, Electrochromatic mirror, Manual A/C blend door actuator |
| 15 | 5 | AdvanceTrac® with RSC switch, Instrument cluster (Run/Start feed) |
| 16 | 10 | BS/AdvanceTrac® with RSC module (Run/Start feed) |
| 17 | 15 | Foglamps |
| 18 | 10 | Auxiliary A/C temperature blend door actuator, Auxiliary A/C front auxiliary control, Turn signal flasher, Electrochromatic mirror, Auxiliary mode motor |
| 19 | 10 | Restraints Control Module (RCM) |
| 20 | 30 | BSM (door locks, liftgate glass release relay), Liftgate glass release motor, Door/Liftgate lock motors |
| 21 | 15 | Instrument cluster (B+), Interior (courtesy) lamps, Puddle lamps (outside mirrors) |
| 22 | 10 | Moonroof switch illumination, Radio (delayed accessory feed), Flip window switch, Flip window motors, EHAM antenna amplifier (navigation radio) |
| 23 | 10 | RH low beam |
| 24 | 15 | Interior demand lamps (front map/dome lamp, 2nd row dome/map lamp, glove compartment lamp, cargo lamp, roof rail lamps, vanity mirror lamps), Battery saver relay coil, Battery saver relay power, Heated Positive Crankcase Ventilation (PCV) valve |
| 25 | 10 | LH low beam |
| 26 | 20 | Horn relay, Horns |
| 27 | 5 | Compass module, Reverse sensing system module, Brake shift interlock solenoid, Overdrive cancel switch, Air suspension module (Run/Start sense) |
| 28 | 5 | PCM relay coil, SecuriLock transceiver, Heated PCV valve relay coil |
| 29 | 30 | Trailer tow electric brake controller, Trailer tow 7–wire connector (electric brake) |
| 30 | 25 | Air suspension module (air spring solenoids and height sensors), PCM (4×4 transfer case clutch) |
| 31 | 20 | Radio (B+), Subwoofer |
| 32 | 15 | Catalyst Monitor Sensors (CMS), Transmission solenoids, Canister vent solenoid, HEGO sensors, VMV solenoid, A/C compressor clutch relay coil, CMCV, VCT actuators |
| 33 | – | Not used |
| 34 | 15 | PCM, Fuel injectors, Mass Air Flow (MAF) sensor |
| 35 | 20 | Instrument cluster high beam indicator, High beam headlamps |
| 36 | 10 | Trailer tow right turn/stop lamps |
| 37 | 20 | Cargo area power point |
| 38 | 25 | Rear wiper motor, Washer pump (rear window wash) |
| 39 | 20 | Console power points (front and rear of console), Instrument panel power point (bench seat) |
| 40 | 20 | DRL relays, DRL foglamps, DRL headlamp relay coil, Headlamp switch (headlamps), Multifunction switch (flash-to-pass), BSM (autolamp headlamps relay), High beam relay coil, Fuse 25 (LH low beam), Fuse 23 (RH low beam) |
| 41 | 20 | Cigarette lighter, OBD II diagnostic connector |
| 42 | 10 | Trailer tow left turn/stop lamps |
| 101 | 30 | Starter motor relay, Starter motor solenoid |
| 102 | 30 | Ignition switch power |
| 103 | 30 | ABS/AdvanceTrac® with RSC module (pump motor) |
| 104 | 30 | LH 3rd row seat relay, LH 3rd row seat switch, LH 3rd row seat motor |
| 105 | 30 | Spare |
| 106 | 30 | Trailer tow battery charge relay, Trailer tow 7–way connector (battery charge) |
| 107 | 30 | Auxiliary A/C blower relay, Auxiliary A/C blower motor |
| 108 | 30 | Passenger seat motor switch |
| 109 | 30 | Driver seat motor switch (non-memory), Memory module, Power memory mirrors, Adjustable pedals switch and motor |
| 110 | 30 | Spare |
| 111 | 50 | Air suspension compressor, Air suspension compressor relay |
| 112 | 30 | ABS/AdvanceTrac® with RSC module (valves) |
| 113 | 30 | Front wiper motor, Washer pump (windshield wash) |
| 114 | 40 | Rear window defroster relay, Rear window defroster grid, Heated mirrors (Fuse 8) |
| 115 | 30 | Transfer case shift motor, 4×4 relays |
| 116 | 40 | Front blower motor relay, Front blower motor |
| 117 | 30 | RH 3rd row seat relay, RH 3rd row seat switch, RH 3rd row seat motor |
| 118 | 30 | Driver and passenger climate control seat module |
| 401 | 30 | Power windows (circuit breaker), Main window switch, Window motors, Window switches, Moonroof module |
| R01 | Starter relay: Starter motor solenoid | |
| R02 | Delayed accessory relay: Fuse 22, CB 401, Power windows, Switch backlighting, Radio, Moonroof, Flip windows, Navigation antenna amplifier | |
| R03 | Hi-beam relay: Fuse # 35, Hi-beam headlamps, Hi-beam indicator | |
| R04 | Rear window defrost relay: Fuse 8 (heated mirrors), Rear window defroster, Heated outside mirrors, Rear window defroster indicator (climate control head) | |
| R05 | Trailer tow battery charge relay: Trailer tow 7–wire connector (battery charge) | |
| R06 | Front blower relay: Front blower motor | |
| R201 | Trailer tow park lamp relay: Trailer tow 7–wire and 4–wire connectors (park lamps) | |
| R202 | Foglamp relay: Front foglamps | |
| R203 | PCM relay: Fuse 32, Fuse 34, PCM solenoids and sensors | |
| R301 | Trailer tow back-up lamp relay: Trailer tow 7–wire connector (back-up lamps) | |
| R302 | Heated PCV valve relay: Heated PCV valve | |
| R303 | Fuel pump relay: Fuel pump shut-off switch, PCM (fuel pump monitor), Fuel pump, Fuel pump driver module | |
| R304 | Battery saver relay: Roof rail lamps, Vanity mirror lamps, Map/Dome lamp, Glove box lamp, Cargo area lamp, Outside mirror puddle lamps, Instrument cluster (interior lamps) | |
| R305 | Horn relay: Dual note horn |
Detailed fuse box diagram for 2003-2006 Ford Expedition, applicable to 2003 Excursion, listing amperage and function for each fuse to aid in electrical troubleshooting.
How Fuse Issues Can Impact Your 2003 Excursion OBD2 System
While fuses primarily protect electrical circuits, problems within these circuits can sometimes manifest as issues detectable by your 2003 Excursion’s OBD2 system. For example, a blown fuse related to critical sensors or the Powertrain Control Module (PCM) – as seen with fuses 5, 28, 32, and 34 – could lead to error codes when you scan your vehicle using an OBD2 scanner.
Specifically, Fuse 41 (20A) is directly linked to the OBD II diagnostic connector. If you are experiencing issues connecting your OBD2 scanner or are not getting any readings, checking this fuse should be one of your first steps. Similarly, fuses related to the PCM (like fuses 5, 34, and relay R203) are crucial for the overall functioning of the engine management system, which is heavily monitored by the OBD2 system.
By understanding the fuse box layout and the function of each fuse, you can proactively diagnose and resolve minor electrical problems that might otherwise lead to more complex diagnostic procedures via the OBD2 port. Always consult your Ford Excursion owner’s manual for the most accurate fuse information specific to your vehicle trim and options.
