Disconnect IAC motor connector. Check resistance between IAC motor connector terminal No. 2 and either terminal No. 1 or 3. Also check resistance between IAC motor connector terminal No. 5 and either terminal No. 4 or 6. Each resistance should be 28-33 ohms at 68°F (20°C). If resistances are not as specified, replace IAC body assembly. If resistances are as specified, go to next step.
If using lab scope, go to step 4. Engine coolant temperature must be 68°F (20°C) or less. If not, an Engine Coolant Temperature (ECT) sensor that is appropriate temperature can plugged into ECT sensor connector. Turn ignition on (engine off) and listen for IAC motor operation sound. Operational sound should be heard when ignition is turned on and off.
For testing IAC control circuit, see DTC P0505: IDLE CONTROL SYSTEM MALFUNCTION in appropriate SELF-DIAGNOSTICS article.
Using test harness, or backprobing, connect lab scope pick-up, in turn, to IAC motor connector terminals No. 1, 3, 4, and 6. With engine running, compare IAC motor waveform to normal waveform. See Fig 1.

Fig 1: Identifying Normal IAC Motor Waveform

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

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

Idle Air Control (IAC) Motor