Idle Air Control (IAC) Valve

Warm engine to normal operating temperature. Ensure idle speed is correct. See IDLE SPEED & MIXTURE in the ADJUSTMENTS article.
Apply parking brake and place transmission/transaxle in Neutral. Install Jumper Wire (SST 09843-18020) between terminals TE1 and E1 of data link connector No. 1. See Fig 1. Start engine and note RPM.
NOTE: Data link connector No. 1 is located in engine compartment.

Engine RPM should increase to specified RPM for 5 seconds, and then return to idle. See IAC VALVE ENGINE SPEED TESTING SPECIFICATIONS table.

IAC VALVE ENGINE SPEED TESTING SPECIFICATIONS

Application	Engine RPM
Tercel	900-1300

If engine RPM is not as specified, check IAC valve resistance and operation. If engine RPM is within specification, remove jumper wire. Turn ignition off.
To check IAC valve resistance, ensure ignition is off. Disconnect electrical connector from IAC valve located on lower area of throttle body. Using ohmmeter, measure resistance between terminal B+ or +B and each remaining terminal. See Fig 2.
Replace IAC valve if resistance is not within specification. See IAC VALVE RESISTANCE SPECIFICATIONS table.
To check IAC valve operation, remove IAC valve from throttle body. Connect battery voltage and ground to proper terminals and ensure valve opens and closes. See Fig 3. Replace IAC valve if defective.
If IAC valve resistance is correct and operates correctly, check wiring circuit between Engine Control Module (ECM) and IAC valve. See ECM LOCATION table. See wiring diagram in the WIRING DIAGRAMS article.

IAC VALVE RESISTANCE SPECIFICATIONS

Application

Ohms

Cold ⁽¹⁾

17.0-24.5

Hot ⁽²⁾

21.5-28.5

⁽¹⁾	Cold is with temperature of 14-122°F (-10 - 50°C).

⁽²⁾	Hot is with temperature of 122-212°F (50-100°C).

Fig 1: Installing Jumper Wire In Data Link Connector No. 1

Fig 2: Checking IAC Valve Resistance

Fig 3: Checking IAC Valve Operation