1993 Subaru Justy BaseFACTORY OEM SERVICE PROCEDURE

Code 24: Idle Speed Control Solenoid Valve

NOTE: Refer to illustration for ECU connector and terminal identification. See Figure .
  1. Connect test mode connector. Connector is located under left side of instrument panel. See Figure . Turn ignition on. Check Idle Speed Control (ISC) solenoid valve for operating vibration. If ISC solenoid valve operates properly, check for poor ECU connector contact. Repair connector and/or wiring harness as necessary. If connector and wiring harness are okay, replace ECU. If ISC solenoid valve does not operate properly, go to next step.
  2. Disconnect ISC solenoid valve sub-harness connector. See Fig 1 . Turn ignition on. Measure voltage between ground and terminal No. 2 of sub-harness connector. If voltage is more than 9 volts, go to next step. If voltage is less than 9 volts, repair ISC power circuit as necessary.
    Fig 1: ISC Solenoid Valve Sub-Harness Connector Terminal ID (Justy)
    G93F80684Courtesy of SUBARU OF AMERICA, INC.
  3. With temperature 68°F (20°C), measure resistance between terminals No. 1 and 2 of sub-harness connector. See Fig 1 . If resistance is 20-30 ohms, go to step 5). If resistance is not 20-30 ohms, go to next step.
  4. With temperature 68°F (20°C), measure resistance between ISC solenoid valve terminals. If resistance is 20-30 ohms, repair sub-harness as necessary. If resistance is not 20-30 ohms, replace ISC solenoid.
  5. Disconnect ECU connectors. Measure resistance between ECU and ISC sub-harness connectors. Refer to the ISC SOLENOID VALVE RESISTANCE SPECIFICATIONS  table. If resistance is as specified, go to next step. If resistance is not as specified, repair connector and/or wiring harness as necessary.
    ISC SOLENOID VALVE RESISTANCE SPECIFICATIONS

    Measure Between Terminals Ohms
    No. 24 (1) & No. 1 (2) Less Than One
    No. 24 (1) & Ground Infinite
    No. 13 (1) & Ground Less Than 10
    No. 26 (1) & Ground Less Than 10
    (1) Measure at ECU connector F119.
    (2) Measure resistance at ISC sub-harness connector. See Fig 1 .
  6. Reconnect ISC solenoid valve and ECU connectors. Disconnect test mode connector. Turn ignition on. Measure voltage between ground and ECU connector F119, terminal No. 24. If voltage is more than 8 volts, check for poor ECU connector contact. Repair connector and/or wiring harness as necessary. If connector and wiring harness are okay, replace ECU. If voltage is less than 8 volts, repair ISC sub-harness as necessary.
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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.