DTC P1507 (ISC_SHI): Idle Control System Malfunction (Fail-Safe)

1998 Subaru Forester L, StandardSECTION DTC P1507 (ISC_SHI): Idle Control System Malfunction (Fail-Safe)
  1. Connect scan tool. Retrieve DTC(s). If DTC P0505 also exists, diagnose DTC P0505. DO NOT  diagnose DTC P1507. If only DTC P1507 is set, go to next step.
  2. Start and allow engine to idle. Check intake manifold, idle air control (IAC) valve and throttle body for loose installation or cracked gaskets. Check by-pass hoses for loose connection or cracking and vacuum hoses for disconnection or cracking. Repair as necessary. If no damage is noted, replace IAC valve.
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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.