How to Manually Error-Test My Ford Truck


Not all Ford trucks can be manually error-tested. After 1996, the second generation of On-Board Diagnostics became standardized for all car and light trucks. Accessing the OBD-II system requires diagnostic hardware. The error codes themselves are alpha-numeric, which is logistically difficult to flash through the truck's check engine light. Manual code retrieval works only for Fords using Electronic Engine Control-Fourth Version. Those vehicles run from 1983 to 1995. Still, the process is not that complicated, and the codes can be retrieved in less than 15 minutes.

Things You'll Need

  • Jumper wire
  • Warm up the Ford truck's engine. You can either let the vehicle idle, or you can drive it around. Either way, the engine needs to be truly warmed, which means the air conditioner needs to stay off.

  • Turn the engine off and release the Ford's hood. Prop the hood open and look for two outlets towards the rear of the engine, near the fire wall. One outlet features six sides and six slots. It is called the Self-Test Outlet. Next to it, you will find a single slot on a twisted braid of wire. That is the Self-Test Input.

  • Connect the STI and the STO with a length of jumper wire. Place one end of the wire into the STI. Place the other end into the STO's grounding slot, which should be located in a row of four openings. The slot you need is the center-left.

  • Return to the Ford truck's driver seat. Place your key into the truck's ignition and turn to "On." Leave the engine off. This will initiate the EEC-IV self-testing procedure. Grab a pen and a slip of paper and keep your eyes focused on the check engine light.

  • Count how many times the Ford truck's check engine light goes on and off. This will represent a two-digit EEC-IV fault code. The first number will be conveyed through long flashes. The second number will be conveyed through shorter flashes. For instance, EEC-IV code 24 is two long flashes and four short flashes. Write the code numbers down.

  • Turn off the Ford truck's electrical system once the system has cycled through all the error codes. Remove the jumper wire from the STI and STO. Close the hood over the engine.

  • Look up definitions for all of the codes you have written out. Ford's EEC-IV codes are not in the owner's manuals. You can locate definitions in a Haynes manual or online. These definitions will give you an indication of what repairs are needed. If you choose not to complete the repairs, bring the truck and code list to your mechanic. It should keep you from being charged diagnostic fees.

Related Searches


  • "Haynes Repair Manual: Ford Pickups and Bronco, 1973-1979"; John Haynes; 1988
  • "Haynes Repair Manual: Ford: Ranger/Bronco II 1983-90"; Todd W. Stidham; 1998
  • Photo Credit Car dashboard image by Andrejs Pidjass from
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