How To Use Circuit Tests: Notes

1985 Ford Mustang LX, 2D Hatchback, 5.0 FSECTION Notes
  1. Do no run any test unless codes have been set during QUICK TEST. Make sure all non-EEC related faults are corrected. DO NOT  replace any part unless directed to do so. When more than 1 service code is received, start with the first code displayed.
    NOTE: Procedures in the TESTING section of this article are not in absolute numerical order. Procedures not related to this engine have been removed to eliminate confusion.
  2. DO NOT  measure voltage or resistance at ECA or connect any test lamps to it, unless specified. All measurements are made by probing the REAR of the computer. Isolate both ends of a circuit and turn key OFF whenever checking for shorts or continuity, unless specified.
  3. Disconnect solenoids and switches from harness before measuring continuity, resistance or applying 12 volts. Follow each test step in order until fault is found. After each repair, check all component connections and repeat Circuit test.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.