1. Simple Mechanical Issues:
* Broken or disconnected cable: Older vehicles (though less common on this model year) might have a throttle cable. Check for breaks, disconnections, or severe fraying.
* Stuck pedal: Something might be physically jamming the pedal. Check for debris, damage, or binding.
2. Electronic Issues (More Likely on a 2003):
* Throttle Position Sensor (TPS): This sensor tells the PCM (Powertrain Control Module) how far the pedal is depressed. A faulty TPS can send incorrect signals, resulting in no response or erratic acceleration. This is a HIGHLY likely culprit.
* Pedal Position Sensor (PPS): Similar to the TPS, but this sensor is specifically located within or near the accelerator pedal assembly. It might be a separate component or integrated with the TPS.
* PCM (Powertrain Control Module): The "brain" of the vehicle. A faulty PCM can cause a myriad of problems, including a non-functional gas pedal. This is less likely than a sensor issue but still possible.
* Wiring harness: Damaged, corroded, or pinched wires between the pedal, sensors, and PCM can interrupt the signal. Look for any obvious damage along the wiring routes.
* Accelerator Pedal Assembly (APM) / Electronic Throttle Control (ETC) system: The 2003 F-250 likely uses an electronic throttle system, meaning there's no physical cable. A problem with the entire assembly could prevent proper signal transmission. This includes internal components within the pedal assembly itself.
* Fuse/Relay: While less common, a blown fuse or faulty relay related to the throttle control system could interrupt power. Check your owner's manual for relevant fuse and relay locations.
3. Less Likely but Possible Issues:
* Fuel System Problems: Though the pedal isn't directly involved, severe fuel delivery issues (blocked filter, fuel pump failure) can prevent the engine from responding even if the pedal is depressed.
* Transmission Problems: In extremely rare instances, a significant transmission issue might cause the engine to not respond to throttle input.
Troubleshooting Steps:
1. Visual Inspection: Start by examining the accelerator pedal, cable (if present), and wiring harness for any obvious problems.
2. Check fuses and relays: Consult your owner's manual to locate the relevant fuses and relays.
3. Have the codes scanned: Use an OBD-II scanner to retrieve any diagnostic trouble codes (DTCs) stored in the PCM. These codes can pinpoint the specific problem area. A professional-grade scanner will give you more detail than a basic code reader.
4. Professional Diagnosis: If you can't identify the problem with the above steps, it's best to take your truck to a qualified mechanic or Ford dealership for diagnosis and repair. Working on the electronic throttle system without proper knowledge can be dangerous.
Remember safety first. If you're not comfortable working on your vehicle's electrical system, don't attempt repairs yourself. The TPS and PCM are relatively expensive parts, so proper diagnosis is critical before replacing parts.
