Before testing A/C idle-up system, ensure hoses at A/C idle-up valve are not damaged or clogged. A/C idle-up valve is located on end of air intake chamber, near throttle body. See Fig 1.
Ensure idle speed is correct with engine at normal operating temperature. See IDLE SPEED & MIXTURE in ADJUSTMENTS article. Apply parking brake. Place transaxle in Neutral.
With engine idling, turn A/C on. Install Jumper Wire (SST 09843-18020) between terminals "TE1" and "E1" on DLC-1. See Figure.
Engine idle speed should increase for approximately 3 seconds and then drop to just slightly above normal idle speed and remain at this speed. If idle speed does not increase, proceed to step 6. If idle speed is correct, proceed to next step.
After about 15 seconds, ensure idle speed does not increase more than 100 RPM than idle speed obtained in step 4). If idle speed increases more than 100 RPM, rotate adjusting screw on A/C idle-up valve so idle speed does not exceed idle speed obtained in step 4). See Fig 1. Remove jumper wire from DLC-1. Turn A/C off and remove tachometer.
If idle speed does not increase as specified, check A/C idle-up valve. See A/C IDLE-UP VALVE under IDLE CONTROL SYSTEM. If the A/C idle-up valve operates correctly, proceed to next step).
Remove glove compartment for access to Engine Control Module (ECM). Turn ignition on.
Using voltmeter, check voltage between terminal No. 1 (White/Blue wire) of "E6" connector and chassis ground. See Figure.
Voltage should be 9-14 volts with the ignition on and A/C off. If voltage is not within specification, check for defective EFI main relay or wiring harness between EFI main relay and ECM. See EFI MAIN RELAY under RELAYS. See wiring diagram in WIRING DIAGRAMS article.
If EFI main relay and wiring harness are okay, check ECM ground circuit. If ECM ground circuit is okay, substitute another ECM and recheck system operation.

Fig 1: Identifying Idle Speed Adjusting Screw On A/C Idle-Up Valve

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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.

Safety Warning

A/C Idle-Up System

Use the Manual With the Right Hardware

When to See a Mechanic

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