Diagnosing issues in your 2003 Ford Expedition can sometimes feel like navigating a maze. When your vehicle isn’t performing as it should, understanding where to start looking is crucial. Often, the problem might be simpler than you think, potentially linked to a blown fuse or a diagnostic trouble code readable through your OBD2 port. This guide will help you understand the fuse box layout of your 2003 Ford Expedition and how it relates to potential OBD2 codes, empowering you to troubleshoot common electrical problems effectively.
Your 2003 Ford Expedition’s main fuse box, also known as the power distribution box or passenger compartment fuse panel, is conveniently located inside the vehicle. To access it, look under the right-hand side of the instrument panel, in the passenger footwell area. This location houses fuses and relays that protect various electrical circuits throughout your vehicle.
Knowing the location is just the first step. To truly utilize your fuse box for diagnostics, you need to understand the function of each fuse and relay. The following table provides a detailed breakdown of the fuses within the passenger compartment fuse box of your 2003 Ford Expedition. This information is invaluable when trying to pinpoint the cause of electrical malfunctions, which can sometimes trigger your vehicle’s check engine light and store OBD2 codes.
| № | 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 |
Understanding the Link Between Fuses and OBD2 Codes
While this guide primarily focuses on the fuse box, it’s important to understand how fuse problems can be related to OBD2 (On-Board Diagnostics II) codes. Your 2003 Ford Expedition is equipped with an OBD2 system that monitors various sensors and systems throughout the vehicle. When a malfunction is detected, the system may store a diagnostic trouble code (DTC) and illuminate the check engine light.
A seemingly complex OBD2 code issue might sometimes boil down to a simple blown fuse. For example, if you’re experiencing issues with your fuel pump and your OBD2 scanner is showing codes related to fuel delivery, checking the fuel pump fuse (Fuse 12 in the table) should be one of your first steps. A blown fuse interrupts the power supply to the fuel pump, causing it to malfunction and potentially triggering related OBD2 codes.
Similarly, issues with other systems like your Expedition’s air conditioning, lighting, or even engine management components could be fuse-related. Before assuming a major component failure and delving into complex OBD2 diagnostics, always take a moment to inspect the relevant fuses. Fuse 41 in the passenger compartment fuse box is specifically for the OBD II diagnostic connector itself. If this fuse is blown, you might not even be able to connect your OBD2 scanner to read codes!
Using This Guide for Effective Troubleshooting
- Identify the Problem: Notice a system malfunction in your 2003 Ford Expedition. Is it the wipers not working, lights flickering, or the engine running rough?
- Consult the Fuse Diagram: Refer to the table above to locate the fuse(s) associated with the malfunctioning system. For example, for wiper issues, check Fuse 1 and Fuse 113 (in the power distribution box under the hood, not detailed in this specific diagram but worth noting for a comprehensive approach).
- Inspect the Fuse: Locate the fuse in your vehicle’s passenger compartment fuse box and visually inspect it. A blown fuse will typically have a broken wire inside.
- Replace if Necessary: If the fuse is blown, replace it with a fuse of the same amperage rating.
- Check for OBD2 Codes (If Applicable): If the issue triggered your check engine light, use an OBD2 scanner to read the stored codes. After addressing the fuse issue, clear the codes and see if they reappear.
By combining this fuse box diagram knowledge with OBD2 code scanning, you can approach troubleshooting your 2003 Ford Expedition in a more systematic and efficient manner. Remember to always consult your vehicle’s repair manual for detailed procedures and safety precautions when working on your car’s electrical system.
