How to Test Ignition Control Module with Multimeter

Having problems with your car causes a lot of things to run through your mind. You don’t know exactly what the issue is and fear that it could be a huge problem you don’t want to deal with.

Some faults are easier to diagnose and take care of than others, and one of these is problems with your ignition control module.

This article takes you through all you need to know about this component. Let’s get right in.

What Is An Ignition Control Module

An ignition control module (ICM) is a component within your ignition system that controls the process of turning the engine on and off. It does this by feeding the ignition coils with current and generating the appropriate amount of energy to power up the spark plug and ignite the fuel mixture for the engine to function well.

The ignition control module is also controlled by the ECU, as the ECU sends signals for ignition timing through the distributor. 

From this, you see that your vehicle is not expected to start and function properly if the ignition control module is bad. However, how do you know when it is bad? 

Symptoms Of A Bad Ignition Control Module

Here are a few pointers to a bad ignition system.

1. Illuminated Engine Light 

The Electronic Stability Control (ESC) module constantly monitors all parts of your car for issues. When components within your engine have faults, just like your ignition control module, the ESC turns on the engine light on the dashboard.

2.  Overheating

A bad ICM causes overheating in your vehicle. When this happens, your engine stops working until it is given enough time to cool off.

3. Acceleration Problems

When your Ignition control module is bad, you may experience a series of issues with your acceleration. These include your car jerking or vibrating when the acceleration pedal is pressed, slow responses when you increase your car speed or a lack of power with accelerations.

4. Engine Stalling

This is mostly concerned with a lack of spark from your spark plugs. A faulty ICM does not produce any spark and this causes your engine to stall. 

5. Engine Misfiring

The ICM is a crucial component within your combustion system and when it develops faults, your engine keeps misfiring due to incomplete combustion.

Some other symptoms of a bad ignition control system include difficulty starting the car and problems powering car accessories.

Tools Needed To Test Ignition Control Module

There are multiple ways to test your ignition control module and these methods need equipment to be implemented.

The tools you need include 

• A digital multimeter, which is also great for testing other electronic components
• Wire piercing probes
• A wiring diagram of your vehicle to easily locate components
• A 12-volt test light
• An assistant

How To Test Ignition Control Module With Multimeter

To test your ignition control module with a multimeter, you place the red lead on the positive ignition coil terminal and ground the connection with the black lead. Your assistant then cranks up the engine and you check if the multimeter reads between 0.4 and 2 ohms. 

Before you do this, however, there is a whole lot more to know and these steps will be explained further. 

1. Testing Through The Ignition Coils

Cars come with varying numbers of ignition coils and these are determined by the number of cylinders in the vehicle. Four-cylinder engines come with two coils, six-cylinder engines come with three coils and a V8 engine comes with four coils.

Regardless of these, however, there is only one primary negative and one primary positive terminal. These are the two components you want to check.

If you are not clear about all these, here is a video that proves helpful.

To test your ignition control module through the coils, you place your red lead on the positive terminal and ground the connection with the black lead. Your assistant powers up the engine and you wait for readings on your multimeter.

You repeat this process with your black multimeter lead by connecting it to your negative terminal, grounding the connection with your positive lead, and waiting for a reading when your assistant cranks up the engine.

If the multimeter does not produce any readings from the steps mentioned above, then your ignition control module is likely faulty.

2. Checking Through The Ignition Control Module Wires

Inspecting your wires is one thing you want to do when you don’t see problems with your ignition coils.

To test for problems within your ICM wiring, you set your multimeter dial to ohms and pierce your ICM wires with the multimeter leads. Here, you want to check for continuity within your wiring system between your ICM and spark plug and determine whether it is the source of the problems.

While doing this, you don’t have to start the engine. You just turn the ignition key to the “on” position and use your multimeter leads to inspect each wire for continuity.

If your multimeter produces no reading, then your wiring is bad and it needs to be changed. This is an easier issue to fix than diving into the ICM itself.

Inspecting Spark Plugs

Using a 12-volt test light, check for current within your spark plug. To do this, you place your test light on the spark plug terminal and see if the light flickers when your assistant cranks up the engine.

If the light flickers, your spark plug is good. In case it doesn’t, then the plug needs to be changed or you need to engage in further checks.

Fixing The Ignition Control Module

Repairing an ICM is easy where the faults have been found in the spark plugs or wiring system. If the problem comes from the coils, then there may be a need to change the whole ignition control module. 

A professional mechanic is best for this and you can expect costs between $290 and $400.

Frequently Asked Questions