Idle Air Control (IAC) Valve
- Check idle speed following procedures in ADJUSTMENTS - 1.8L article. If idle speed is as specified, go to next step. If idle speed is not as specified, follow procedures in DTC P0505 in BASIC TESTING - 1.8L article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they malfunction, also perform procedures in TESTS W/CODES - 1.8L article.
- With engine running, turn headlights on. If idle remains at specified idle speed, system is okay. If idle speed is not within specification, go to next step.
- Ensure engine is at normal operating temperature. Turn ignition off. Disconnect IAC valve harness connector. Start engine and note idle speed. Turn ignition off. Reconnect IAC valve harness connector. Using a fused jumper wire, backprobe PCM harness connector "B", terminal No. 24 to ground. Start engine and note idle speed. If idle speed is higher with terminal grounded, system is okay. If idle speed remains at same speed, go to next step.
- Turn ignition off. Disconnect IAC valve harness connector. Using an ohmmeter, measure resistance between IAC valve terminals. If resistance is 11-14 ohms at 68°F (20°C), go to next step. If resistance is not as specified, replace IAC valve. Retest system.NOTE: Incorrect jumper connections made to IAC valve will result in damage. Ensure all connections are made correctly. DO NOT reverse leads during test.
- Start engine and note idle speed. Using fused jumper wires, connect battery voltage to terminal No. 1 and ground terminal No. 2 of IAC valve terminals. See Fig 1 . If idle speed increases, check IAC valve harness for an open or short circuit. If idle speed did not change, replace IAC valve. Retest system.