How to Reset a Ford Expedition's Check Engine Soon Light

by Richard Rowe
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All Ford Expeditions use the same computer program and code set to record and diagnose engine malfunctions. This code set is known as OBD-II, or On-Board Diagnostics, Series 2. As the name suggests, the program continually monitors the engine through dozens of sensors to warn the driver if any of them exceed the factory parameters. If anything goes wrong with the engine, the computer will illuminate the check engine light (CEL). If the light stays on, the fault is ongoing. If it goes off, the problem is intermittent, but the computer will store the code for later diagnostics.

Step 1

Open the hood of your vehicle. Locate the battery and identify the negative battery terminal. This is the one with the black wire attached to it.

Step 2

Slip a flat-head screwdriver under the plastic cover over the terminal and pry it loose.

Step 3

Slip a 1/2-inch socket over the horizontal nut on the battery terminal clamp and turn it counterclockwise. If the entire bolt rotates in the terminal housing, hold the square head with a 1/2-inch wrench while turning the nut.

Step 4

Loosen the terminal nut intil you see 1/8 inch of space between it and the terminal. Wiggle the terminal back and forth while applying firm upward pressure. Continue doing so until the cable is free of the battery.

Step 5

Wrap the terminal in a clean, dry towel or shop rag and set it off to the side of the battery. Leave it there for five minutes. The computer should reset after three, but give it five just to be safe.

Reinstall the negative cable on the battery and replace the cover.


  • This procedure will clear any active codes, but it won't fix the problem that caused the CEL. If the CEL reappears after this procedure, you need to take the truck to your local dealership to have the code read and diagnosed. While you're there, have them clear the stored codes, electronically reset the computer and see if the fault reappears. Some auto parts stores will also do this for you free of charge, with the same result.

Items you will need

  • Metric and standard socket set
  • Metric and standard wrench set
  • Flat-head screwdriver

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