Start engine, and warm to operating temperature. Check idle speed. If idle speed is excessive, disconnect IAC valve harness connector. Idle speed should drop.
If idle speed does not drop, check for battery voltage at IAC valve connector terminal "A" (Green/Yellow wire). If battery voltage is present, go to next step. If battery voltage is not present, check fuses and harness for open circuit.
Turn ignition off. Disconnect ECM harness connector. Check harness continuity between IAC valve connector terminal "B" (Blue wire) and ECM terminal No. 101.
Continuity should exist. If continuity does not exist, repair wiring as necessary. If harness tests okay, test IAC valve and inspect ECM connector terminal pins for corrosion or damage.

IDLE SPEED SYSTEM INPUT SIGNALS

Application

Model Usage

A/C Clutch Signal

⁽¹⁾ J30

Battery Voltage

J30

Closed Throttle Position Switch

J30

Crankshaft Position Sensor

J30

Engine Coolant Temperature

J30

Ignition (START) Signal

J30

Park/Neutral Switch

⁽²⁾ J30

Power Steering Pressure Switch

J30

Throttle Position Sensor

J30

Vehicle Speed Sensor

J30

⁽¹⁾	Signal received from automatic A/C amplifier.

⁽²⁾	Signal received from transmission control unit.

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

System Test