Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Idle Speed Control (ISC) System (Swift DOHC)
- Warm engine to normal operating temperature. With engine running, use stethoscope and check for operating sound at ISC solenoid. The ISC solenoid is mounted on intake manifold, between valve covers.
- If operating sound was heard, go to step 4). If no operating sound was heard, check ISC solenoid. See appropriate IDLE SPEED CONTROL (ISC) SOLENOID under IDLE CONTROL SYSTEM in this article. Replace ISC solenoid if defective. If ISC solenoid was okay, go to step 3).
- Check for open or short in Red/White wire between ECM and ISC solenoid. Check for defective connection at ISC solenoid and ECM. If wiring and connections are okay, substitute ECM and recheck.
- With engine idling, pinch upper hose on ISC solenoid closed. Note if engine speed decreases. If engine speed decreases, go to step 5). If engine speed does not decrease, check for restricted air passages on ISC solenoid.
- Ensure idle speed is within specification. See ADJUSTMENTS
article. With idle speed correct, ensure the following conditions are present:
- Idle speed remains at 800-900 RPM with headlights on.
- Ensure ISC solenoid does not operate (operating sound is not heard) for only a few seconds after warm engine is started.
- Increase engine speed to 4000 RPM, quickly close throttle valve and ensure ISC solenoid does not operate (operating sound is not heard) for only a few seconds.
If all conditions are met, system is operating correctly. If all conditions are not met, substitute ECM and recheck.
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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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