Idle Air Control (IAC) System Inspection: Troubleshooting

IDLE AIR CONTROL - TROUBLESHOOTING

Step	Action	YES	NO
1	Check engine idle speed and IAC duty referring to IDLE SPEED / IDLE AIR CONTROL (IAC) DUTY INSPECTION . Is idle speed / IAC duty within specification?	Go to Step 2.	Go to Step 3.
2	Is engine idle speed kept specified speed even with headlights turned ON?	System is in good condition.	Go to Step 3.
3	Check IAC valve referring to IDLE AIR CONTROL (IAC) VALVE AND FAST IDLE AIR (FIA) VALVE ON-VEHICLE INSPECTION and IDLE AIR CONTROL (IAC) VALVE INSPECTION . Is check result as specified?	Go to Step 4.	IAC valve malfunction, "BLU/BLK", "LT GRN/BLK", "PPL/BLK", "GRY/BLU" or "PPL/YEL" wire open or short or poor coupler connection. If all above are OK, substitute a known-good ECM and recheck.
4	Was idle speed within specification in Step 1?	Check for the following: FIA valve, Vacuum leaks, air inhaling, EVAP canister purge control system, accessory engine load, stuck of PCV valve, clog of idle air passage, MAF sensor, TP sensor, ECT sensor, EGR valve malfunction (leakage from valve seat), A/C signal and transmission range switch signal.	Go to Step 5.
5	Was idle speed higher than specification in Step 1?	Go to Step 6.	Go to Step 8.
6	Check A/C (request) signal circuit referring to INSPECTION OF ECM AND ITS CIRCUITS . (A/C signal can be also checked by using SUZUKI scan tool.) Is it in good condition?	Go to Step 7.	A/C signal circuit open or short, or A/C system malfunction.
7	Was IAC duty less than about 2% in Step 1?	Check FIA valve. Check abnormal air inhaling from intake manifold, throttle body, PCV valve and EVAP canister purge control system.	Check TP sensor (closed throttle position) and ECT sensor for performance. If sensors are OK, substitute a known-good ECM and recheck.
8	Check transmission range switch signal referring to INSPECTION OF ECM AND ITS CIRCUITS . Is check result satisfactory?	Go to Step 9.	Transmission range switch malfunction or its circuits open or short.
9	Was IAC duty more than about 30% in Step 1 of this flow?	Check parts or system which can cause engine low idle. Check FIA valve. Air inhaling from between throttle body and MAF sensor, EGR valve malfunction (leakage from valve seat), accessory engine load, clog of idle air passage and etc.	Substitute a known-good ECM and recheck.