How to Test Ignition Control Modules with a Multimeter (Guide)

In this article, I will teach you to test the Ignition control module with a multimeter. The ignition control module test can be easy when all the instructions are followed.

In general, to test ignition control modules with a multimeter, place the black probe of the multimeter on any vehicle part that is grounded. Now check each terminal using the red probe. Check the multimeter reading during the test. Similarly, don’t forget to crank up the engine while testing.

How to Identify That Your Ignition Control Module Needs Testing

The Ignition control module ICM plays a significant role in a vehicle’s ignition system. This ICM can cause some issues from time to time. So, identifying a bad ignition control module is crucial. But how can I do that?

Here are some signs that indicate a bad ignition control system:

1. Check the Engine Light

Whenever your vehicle suffers from a bad ICM, you can see the check engine light flashing on the dashboard. The check engine light is the most common indicator of a bad ICM.

2. Engine Misfires

An engine misfire can occur because of combustion shortages. A faulty ignition module is one of the main factors for incomplete combustion. (1)

3. Stalling

A faulty ignition control can interfere with this process.

4. Unable to Power Up Accessories

Usually, when your vehicle is in a Running position, all the other accessories will power up. However, if you are dealing with a faulty ignition control module, these accessories won’t power up after adjusting to the Running position.

5. Vehicle Starting Issues

A bad ignition control system can cause some starting issues for your vehicle.

About The Ignition Control Module

icm

ICM is a switch that turns the ignition system Off and On. There is a sensor located inside the distributor.

This sensor sends a signal that can fire up the ignition coil inside the ICM, and the process will produce enough energy for the spark plugs.

Then this energy creates voltage for air/fuel mixture and timed combustion. Eventually, the ICM should control the spark timing accurately.

To sum up, ICM controls the ignition timing, the firing of spark plugs, and the ignition coil pack activities.

Tools Needed

To do the ignition control module test, you will need some tools:

  • A digital multimeter
  • Vehicle wiring diagram
  • A 12V test light
  • Ignition switch for replacement

Note: Apart from the above tools, you will also need someone to help.

How Can I Recognize the Ignition Control Module?

If you are having trouble identifying the ICM, this section will help.

The location of the ICM can change according to the built year and the model. For instance, some vehicles come with a separate ICM; others come with an ICM that the Engine Control Module, aka ECM control.

car engine
Video | hoohoohoblin

Tip: An ECM unit is called the Engine Control Unit(ECU) or the Powertrain Control Module.

However, before rushing into anything, find out whether you have a separate ICM or an integrated ICM.

Usually, the ICM is located in the engine compartment or the distributor housing. You can find a small computer chip from these two locations, which is the ignition module control. The image shown below will give you a better idea of it. (2)

car engine
Video | hoohoohoblin

3-Step Guide on How to Test Ignition Control Module with Multimeter

For this process, we will use a multimeter test. If you follow these steps correctly, it will take around 10 minutes to complete the testing process. So, let’s get started.

Step 1 – Check the ICM’s Current

First, place the multimeter’s black probe on the vehicle’s metal frame. The metal frame should be grounded properly. Otherwise, the test will fail.

Then ask your helper to crank the engine. While the helper is doing that, you must check the different terminals. Place the red probe on each terminal.

We use this simple test to check the current.

mechanic testing car ignition using a multimeter

If the current travels through these terminals, you will get a reading on your multimeter. However, if you do not get any reading, you must replace the entire ignition control module.

Note: Set it to either voltage or resistance mode while testing with the multimeter.

Step 2 – Check the Spark Plugs Current

As you can understand, in the step above, we check the ICM for current. If the current flows through the ICM, you can move on to Step 2.

In this step, we are going to test the ICM spark plugs. For this, you will need the 12V test light. Place the 12V test light into the terminals. While holding the test light, ask your helper to crank the engine. If the test light flickers while the helper cranks the engine, the spark plugs are working properly. Apply the same process to all the terminals.

However, sometimes, the multimeter won’t show any readings. If you are not getting any current, follow Step 3.

Step 3 – Recognize the Faulty Wires

You should follow this step only if you didn’t get any current in Step 2. In this step, we will check for continuity.

First, isolate the wires that have a break or burnt marks.

Then set the multimeter to resistance mode. Test the wires that go from/to spark plugs and the ignition control module. Remember, we are checking for continuity here. Therefore, the individual wires are faulty if the multimeter shows an infinite reading. If the multimeter displays a zero reading, the wires are working properly.

Apply the same procedure to all the wires. You may have to spend some time doing this, but you can easily identify the faulty wires. After recognizing the faulty wires, replace them with new wires.

If you cannot complete the replacement process by yourself, don’t hesitate to get help from a professional.

Deeper Look at the ICM Circuit

During Step 3, you will have to check the wires coming out of the ICM. Most people struggle to identify those wires correctly. So, here is a visual aid for you.

car ignition parts

Pink Wire (A): 12V Power Circuit

White Wire (B): Ignition Control Signal

Black Wire (C): Engine Ground Circuit

White Wire with Black Stripe (D): Switching Signal

Note: As mentioned earlier in this article, the wires and locations may vary depending on the build year and the model.

Wrapping Up

We hope that today, with this article, you got a clear and decisive answer for how to test the ignition module with a multimeter.

Always remember to follow our three-step guide properly. Don’t ignore any of these steps.

For instance, some people jump straight to Step 3. They ignore Steps 1 and 2 completely.






References
(1) combustion – https://www.britannica.com/science/combustion
(2) computer chip – https://www.intel.com/content/www/us/en/history/museum-making-silicon.html

Video Reference

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About Sam Orlovsky

b1d87d2ee85af3e51479df87928bdc88?s=90&d=mm&r=gCertifications: B.E.E.
Education: University Of Denver - Electric Engineering
Lives In: Denver Colorado

Electrical engineering is my passion, and I’ve been in the industry for over 20 years. This gives me a unique ability to give you expert home improvement and DIY recommendations. I’m not only an electrician, but I also like machinery and anything to do with carpentry. One of my career paths started as a general handyman, so I also have a lot of experience with home improvement I love to share.

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