1994 Mitsubishi Precis AutomaticFACTORY OEM SERVICE PROCEDURE

Idle Speed Control Motor

NOTE: For diagnosis and testing information concerning ISC motor position sensor, see TESTS W/CODES article.
  1. Using a stethoscope, listen for operation of ISC motor when ignition switch is placed in ON position. If operation cannot be heard, proceed with following tests.
  2. Disconnect ISC harness connector. Connect a 6-volt power source across ISC motor connectors. Check if motor operates. Reverse power source leads and check if motor operates in opposite direction. Replace motor if does not function properly.
  3. Using DVOM, measure resistance between ISC motor connectors. Resistance should be 5-70 ohms. Replace motor if resistance is not within specification.
  4. This step checks for continuity between ISC motor and ECM. Disconnect ISC motor harness connector and ECM harness connector. Connect a jumper wire between selected ECM harness connector terminal and vehicle ground. See ECM TERMINAL SELECTION  table. Using DVOM, check continuity between ISC harness connector No. 1 (Red wire) and vehicle ground.
  5. Move jumper wire to selected ECM harness connector terminal and vehicle ground. See ECM TERMINAL SELECTION  table. Using DVOM, check continuity between ISC harness connector No. 2 (Orange wire) and vehicle ground. If continuity does not exist, check and repair appropriate circuit. If continuity exists, go to step 6).
  6. If preceding tests do not show any system or component malfunction and ECM is suspected, replace ECM and retest system.
    ECM TERMINAL SELECTION

    Terminal No. (1) ISC Motor Terminal No.
    California (Connector No. C50-4)
    23 1
    10 2
    Federal (Connector No. C50-2)
    1 1
    2 2
    (1) See Figure and Figure .
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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.

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