How To Test The Ignition Control Module?

Nobody wants their car to break down in the middle of nowhere. But if you have been driving for long, you must have received your peak share of vehicle breakdown when you least expect it.

Car breakdown can make you think a lot of things, especially when you don’t know where the problem is coming from and can’t tell if it is a huge or minor issue. But you don’t have to panic when your car develops issues until you track the root cause. Some problems are easier to diagnose than others. An excellent example is ignition control module problems.

In this article, I’ll explain how to test the ignition control module, its symptoms, causes, and how to fix it. But first, what does the ignition control module mean, anyway?

symptoms of bad ignition control module

What is an ignition control module?

The ignition control module (ICM) is a crucial ignition system component responsible for turning on and off the engine. It does this by supplying an appropriate amount of electric flow to the ignition coils, which transmits the power to spark plugs to ignite the combustible air-fuel mixture in the combustion chamber.

Without the supply of electric flow to the plugs, the engine will not start. And if there are inappropriate supplies, the engine will start but will not run optimally.

The ignition control module is not an independent component. It is controlled by the car computer as it sends signals to it in real-time. This shows that your vehicle can’t start and run properly without a lousy ignition control module. Let’s look at the symptoms of bad ignition control module in the next section so you can tell when the system fails.

Symptoms of a bad ignition control module

You can easily tell when you have a bad ignition control module because it has various symptoms. However, you need to know how to check if ignition control module is bad because several other vehicle issues can pose some of the same signs. These symptoms are just a pointer for you to run an ignition control test to confirm if it is the real cause.

Engine warning light

The car computer usually displays the engine warning light on the dashboard whenever it detects issues in the powertrain. Since the ignition control module is a powertrain component, the engine warning light will pop up on the dash whenever it fails.

But since several factors can trigger the engine warning light, do not point accusing fingers at the ICM yet. But to figure out if the ICM is the root cause, diagnose the vehicle and pull out all the stored error codes. If you see P1351 or P06D1, you have a lousy ignition control module.

Engine misfiring

As explained earlier, the ignition control module is a critical ignition system component that sends electrical flow to the ignition coils and plugs. If it malfunctions, it’ll send low electric flow to the plugs, leading to engine misfiring due to an incomplete combustion process.

You may confuse a faulty ICM for a lousy ignition coil or dead spark plugs without proper diagnosis.

Engine stalling

If the ICM fails to send the required electric voltage when needed, the plugs will not ignite the fuel properly. This can prevent the vehicle from starting or cause it to die if combustion issues happen while driving.

It may result in a hard start if you try starting the vehicle again. However, the car will start smoothly if you allow the ICM to cool down before starting it. The root cause could be overheating of the ICM, loose wiring, or corroded connections.

ICM overheating

Overheating on the ignition control module is a clear indication that the module is failing. In some cases, the ICM overheats due to a failing distributor. Ignoring the excess heat for an extended period will eventually cause the ignition control module to fail.

Acceleration defects

One of the common bad ignition control module symptoms in Chevy and other car models is acceleration defects. If the ICM fails, you’ll experience several acceleration issues like jerking, vibration, or engine shaking when you depress the accelerator. These are common signs that show the engine is finding it difficult to function correctly since it is not receiving the required power to work well.

It would be unfair if I failed to mention that several other factors can cause the above symptoms. Therefore, you must diagnose the vehicle whenever you notice the above signs to track the leading cause of the problem. But how do you diagnose a bad module? I’ll explain that in the next section.

4 3 ignition control module test

How to test the ignition control module?

Luckily, you can easily tell when you have a lousy ICM by learning how to test ignition control module with a multimeter or a test light. If you follow the below instructions religiously, you’ll know when the plugs, ICM wiring, or the ICM itself is the culprit.

Tools and Items Needed

Step 1: Find the ICM

The first step is to locate the ICM. The best way to do this is to consult your vehicle-specific service manual or get information online. Also, try to understand the ICM wiring to know what wire goes in and out of the ignition control module.

Step 2: Test the ICM with a multimeter

To test the ignition control module, ground the ignition coil terminal with the black probe and place the red probe on the positive ignition coil terminal. Ask your assistant to crank the engine while you check the reading. It should read between 0.4 and 2 ohms. Any reading aside this range shows you have a dead ignition control module that needs replacement.

Step 3: Check the plugs

It’s possible that the current on the ICM is not getting to the plugs. The only way you can know is by testing the plugs. To do this, get a tester and connect the wire to the battery terminal with the plus sign.

Connect the tester’s tip to the plug terminal and see if the light flickers as your assistant starts the vehicle. If the tester blinks or flickers, the plugs are working fine. But if it doesn’t, check the plug wires and ensure they are okay.

Step 4: Test the wires for continuity

Inspect the wirings if you don’t find electric flow on the ICM and the plugs. That could be the root cause of the problem. Inspect the wires and look for burnt, damaged, corroded, frayed, shorted, or open wires. After that, test the wiring harness that travels in and out of the ignition control module.

If there’s no measurable current flow at all, the ignition control module is bad and needs to be replaced. Re-run the above diagnosis after replacing the ICM.

What causes the ignition control module to fail?

The ignition control modules are more prone to fail when you have excessive heat due to old or failing distributor and shorted ignition coils. However, you can easily resolve the underlying issue by diagnosing and replacing the lousy components responsible for the failure.

The ignition control module has a long-term duration. It is designed to last the life of the vehicle. However, they don’t always reach their shelf life.

How to fix a bad ignition control module?

Repairing a bad ignition control module is easy, especially where the root cause lies within the plugs or the wiring harness. But if the test shows the coil is the cause, you may have to change the ignition control module.

Fixing a bad ignition control module requires changing one or more of the following

  • Faulty plugs
  • Malfunctioning distributors
  • Shorted or open wires
  • Bad ignition control module.

Final Words

The importance of the ignition control module cannot be overemphasized. It is a sensitive part of your car; without the ICM, the entire ignition system is compromised, and the vehicle will not run properly.

Therefore, it is crucial to watch out for the signs listed above. You must, however, test the ICM whenever you notice the symptoms above before pointing accusing fingers. Follow the simplified guides above on how to test the ignition control module religiously if you want an accurate result.

Finally, if you are not a DIYer, contact your mechanic to run a thorough diagnosis and resolve the leading cause of the problem.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

Recent Posts