How To Test Ignition Coils With A Multimeter

Ignition coils act as an electrical transformer that amplifies the battery voltage to generate sparks. If it is faulty, the engine may misfire, backfire, have rough idle, or experience sudden power loss.

You need to test the ignition coils when you see these symptoms. But do you know you can do it using a multimeter and at home?

Read on to learn how to test ignition coils with a multimeter. The steps are easy-to-follow!


Toyota Fascia


Symptoms Of Bad Ignition Coils

Before you think of how to test your car’s ignition coils with a multimeter, you must have suspected that they are faulty. So, what signs should you look for? A bad ignition coil is likely to trigger the following symptoms:

Check Engine Light Comes On

The check engine light is yellow/amber with a symbol of an engine block. Some vehicle models may just illuminate it as the words CHECK ENGINE. This warning light comes on if there is a problem with the engine, including a faulty ignition coil. Using an appropriate OBD2 code reader should disapprove or confirm your worst fear.

Engine Not Starting

Engine hard to start is a common problem caused by the faulty ignition coil. It simply means that spark plugs are not getting enough electrical power to create sparks needed to get your engine running.

See also: Oil On Spark Plug Threads | Diagnose and Fix

Decreasing Fuel Economy

The deteriorating fuel efficiency of your engine results from many factors, and a bad ignition coil is one of them. Even if you don’t usually read your fuel gauge against mileage, it is easy to realize when something is off. Before you blame someone else, check your ignition coils and engine as a whole.

See also: Extreme Ways of Lowering Your Car’s Fuel Consumption

Rough Idle

An engine extracts power from the fuel when the air-fuel mixture in the cylinder explodes, pushing the piston down. That process needs a spark to happen. But with a faulty ignition coil, sparking may be irregular, leading to sudden power loss. Your engine may experience rough idling or jerking when accelerating.

Engine Backfiring

Modern engines are designed with advanced control systems to eliminate backfiring. Backfiring occurs when compressed, air-rich fuel escapes from the cylinders unburned. That is caused by delayed sparking because of faulty ignition coils.

Engine Misfiring

A badly damaged spark plug will affect the ignition coil. There will be no sparking, or it will be irregular, which causes misfiring. This may also trigger the check engine light on the dashboard. However, a defective ignition control module is one of the reasons causing misfiring.

If you experience your car shutting down while driving, there might be something wrong with your ignition system. Try to execute some steps to test an ignition control module or ignition coils to confirm your suspicion.

How To Test Ignition Coils With A Multimeter

If you are a DIYer, taking your car to a mechanic when your ignition coils are faulty is unnecessary. Just use a multimeter following simple steps as described here.

Getting Ready

What do you need to test your ignition coils with a multimeter? Here is the list:

· Your car
· Multimeter
· Toolkit for removing the ignition coils (a wrench or ratchet and socket set)

Step-by-Step Guide for Testing Ignition Coils

You are now set to start testing your coils. But before you get there, refer to your car’s service manual for primary and secondary winding resistance specifications. They will be your reference value.


6 Steps to Test Ignition Colis With a Multimeter


Step 1: Ensure your multimeter is working properly

A multimeter is your primary instrument in this exercise. Check if it is properly working. Its battery should provide enough power needed for accurate measurements.

Step 2: Remove the ignition coils

Give your vehicle enough time to cool before opening the hood to remove the ignition coils. Disconnect the battery by unplugging the clip from the negative terminal. Now, locate the coil pack. They are usually mounted on the engine block. Loosen the mounting bolt to remove each coil for testing.

Step 3: Check the primary winding resistance

Visually inspect the coil for any physical damages. Next, set your multimeter to the auto range or minimum on the ohm scale. Lastly, connect it in parallel to the primary coil. Match the terminals accordingly. That is, positive to positive and negative to negative. Check your car’s manual for the exact location.

Compare the reading with the reference values from your car’s service manual. Your coil needs to be replaced if the measured value is below or above the given range. A zero reading shows a short circuit problem, while an infinite resistance indicates an open circuit.

Step 4: Check the secondary winding resistance

Set your multimeter to auto range or about 20K ohms range and connect it in parallel with the secondary coil. Take the reading and compare it with the reference value from the service manual.

If the measured resistance is higher or lower than the given values, the ignition coils are faulty. You need to replace them.

Step 5: Repeating with other ignition coils

Repeat steps 4 and 5 to test all the coils. You should also check any replacement ignition coils if you have them.

Step 6: Plug the ignition coils back

Once you resolve the issue, you can plug the ignition coils back and test the engine. Start the engine
and listen to the idling sound. You may also step on the accelerator pedal to observe any changes.
https://www.youtube.com/watch?v=SZPiD7nv9Bw&ab_channel=CarsNToys

Conclusion

Observe any symptoms that your ignition coil is faulty and use a multimeter to test it. It is a DIY task that you can complete at home if you have the tools and instruments.

Author: Tim Miller
I’m Tim Miller, an automotive mechanic and blogger from Denver, Colorado. I’m the founder of gmundcars.com. My fan page is facebook.com/autozikcom. I’ve had over 20 years’ experience in car repair and using OBD scanners. My reviews and articles about car repair and maintenance can be found on my own website.

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