1990 Ford Probe LX, AutomaticFACTORY OEM SERVICE PROCEDURE

ISC Motor (MPI)

  1. Turn key off and wait 10 seconds. Disconnect harness from ISC motor. Using ohmmeter, put positive lead on ISC connector VPWR terminal and negative lead on ISC terminal. Resistance should be 7-13 ohms. If not, replace ISC motor.
  2. If resistance is 7-13 ohms, measure resistance between either ISC connector terminal and ISC housing. Resistance should be greater than 10 k/ohms. If not, replace ISC motor. If resistance is greater than 10 k/ohms, go to step 3).
  3. Turn ignition on. Using a voltmeter, measure voltage between ISC connector terminals. If voltage is less than 10.5 volts, repair open circuit and repeat test. If voltage is greater than 10.5 volts, turn ignition off. With ISC connector disengaged, connect Breakout Box (014-00322) and leave processor disconnected.
  4. Measure resistance between breakout box test pin No. 21 and ISC terminal on ISC connector. If resistance is greater than 5 ohms, repair open circuit and repeat test. If resistance is less than 5 ohms, measure resistance between breakout box test pin No. 21 and the following test pins: 40, 46, and 60. If resistance is less than 10 k/ohms, repair short circuit and repeat test.
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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.

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