How to Test an IAC Valve with a Multimeter (5-Step Guide)

Idle air control regulates the flow of air into the engine and the amount of gasoline burned by your vehicle. A bad IAC can cause poor gas mileage, higher emissions, and other issues. If you encounter these issues, there is definitely a fix for that. All you need to have is a multimeter, which you may already have in your home.

In general, these five steps will help you test an IAC Valve with a Multimeter:

  • Step 1: Access the IAC valve.
  • Step 2: Turn off the IAC valve.
  • Step 3: Disconnect the vehicle’s IAC valve.
  • Step 4: Inspect the IAC valve.
  • Step 5: Test the IAC valve’s resistance.

Now, I will further discuss in this guide how these steps work.

Test your IAC Valve with a Multimeter in 5 Steps

testing using multimeter

Before we proceed to test the IAC, let us first prepare the equipment needed:

  • Multimeter Test (Digital)
  • Vehicle Scanner for Professionals
  • Pipe Cleaners or Q-Tips
  • Cleaner for the Throttle Body and Intake
  • Service Manual for Vehicles

Note that the throttle body cleaner contains a small amount of lubrication for the throttle body’s moving components. Never use the throttle body cleaner on the hardware of the brake system.

Step 1: Get access to the IAC valve. You can find its location in the vehicle service manual. (1)

Step 2: Turn off the IAC valve. Locate the electrical connector for the IAC valve and unhook it.

Step 3: Disconnect the vehicle’s IAC valve. To remove the IAC valve, follow the procedure outlined in the vehicle service manual.

Step 4: Inspect the IAC valve. Test IAC for carbon build-up, corrosion, or dirt on the valve and the mounting point. Inspect the pintle and mounting position of the IAC motor for damage. (2)

Step 5: Check the IAC motor’s resistance. Use the IAC valve’s specifications from the vehicle service manual as a guide for testing the IAC valve with a multimeter against the electric terminal pins on the IAC valve’s electrical connector. If the reading is within the specs, the valve is likely to be in good working order and the problem is elsewhere. Replacement is the other option if the reading does not meet the specifications.

Note that a new seal may or may not be included with the new IAC valve. To avoid vacuum leakage or a coolant leak when the coolant runs through the IAC valve body, remember to replace the seal whenever a sealed item is removed from the engine.

Failing Idle Air Control: Its Symptoms

air control valve

When an idle air control valve breaks, it can result in various problems and, in some situations, leave the vehicle undrivable. A malfunctioning IAC usually causes several indications that raises these issues:

Changes in Idle Speed Rate

Irregular idle speed rate is one of the most prevalent symptoms of a faulty idle air control valve. The idle air control valve is set up to manage and maintain a steady engine idle speed. The idling rate might be thrown off if the valve malfunctions or has complications. This can cause a high or low idle speed or a surging idle speed that climbs and falls frequently.

Check Engine Light Illuminated

light illuminate

An illuminated Check Engine Light is also one of the signs of a possible problem with the idle control valve. If the IAC control module detects a problem with your idle air control valve signal, the Check Engine Light will light up to alert the driver. A broad range of issues can cause the Check Engine Light to illuminate, thus having the computer examined for trouble codes is strongly advised.

Stalled Engine

Engine stalling is another more dangerous indication of an idle IAC valve problem. If the IAC control valve breaks entirely, the vehicle may lose its air source, making it impossible to maintain normal idling. This will cause the engine to stall while running, and in certain situations, the engine will not idle at all and will stall as soon as it is started.

Rough Idle of the Engine

A regular healthy idle air control valve in your car will provide smooth idling. When there is a reason for a bad IAC, the engine runs rough and rattles from strong vibrations when the vehicle is stopped with the engine running. A rougher idling state is produced by less airflow entering due to an unstable situation caused by corroded electrical connections or fluid leaks preventing it from functioning properly.

Under Load Stalling

The bad IAC may stall on its own at times, but you may force it to restart by increasing the load. Turning up your heat or air conditioner, for example, when you have a defective idle control valve (IAC), causes the engine to stall immediately and may also drag one side of the steering wheel – keep this in mind, and don’t switch off anything while driving!

Before you go, you may check other learning guides below. Until our next article!

(1) vehicle –
(2) carbon –

About Sam Orlovsky

b1d87d2ee85af3e51479df87928bdc88?s=90&d=mm&r=gI realized early on carpentry was a huge passion for me and I’ve stayed in the industry for over 20 years now. This gives me a unique ability to really be able to tell you what the best tools and recommendations are. I’m not only a carpenter but I also like machinery and anything to do with electrics. One of my career paths starting off was as an apprentice electrician so I also have a lot of experience with electrical products and anything related.