How to Test an ignition coil Step by Step Full Guide In 2023

Test an ignition coil – The ignition coil, an essential part of every vehicle’s ignition system, is in charge of supplying power to the spark plugs. A vehicle’s ignition coil can require replacement if it struggles to start, stalls frequently, or misses frequently. Fortunately, a quick test can indicate whether the ignition coil is working properly and whether a trip to the mechanic’s workshop or auto parts store is necessary. To begin, refer to Step 1 below.

If you’re having trouble starting your car, or if it just won’t start at all, it’s time to test your ignition coil. By testing your ignition coil, you can determine the cause of the problem and take the necessary steps to fix it. In this blog post, we’ll provide a step-by-step guide on how to test an ignition coil and help you get started troubleshooting your car. So read on to learn how to test an ignition coil and get started fixing your car!

How to Test an Ignition coil?

If your car won’t start, there’s a good chance that your ignition coil is faulty. An ignition coil is a small device that helps to start your engine by firing the spark plugs. If the ignition coil isn’t working, the sparks won’t reach the plugs and your car won’t start. In this blog post, we will show you how to test an ignition coil and diagnose any problems with it. We will also provide instructions on how to replace an ignition coil if necessary. So if your car won’t start, be sure to check your ignition coil first.

Basic testing can be perform to attempt to pinpoint the issue if you suspect that the ignition coil of your vehicle is defective. Ignition coil failure or damage can result in engine misfires, stalling, poor performance, and reduced fuel economy. When an ignition coil is completely defective, a vehicle, especially one with four cylinders, may not start at all. You should test each of your coils to determine which one is causing problems if you are experiencing an issue with the ignition coil. To perform an ignition coil test, follow these steps.

How to Test an ignition coil Step by Step Full Guide In 2023

How to Test an Ignition coil Details

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Types of ignition Coils

There are a variety of ignition systems with ignition coils, but all of them take energy from the battery (usually 12 volts) and convert it to a voltage high enough to ignite the engine (50,000 volts or more). This voltage either travels from the single ignition coil into a distributor, from the coil itself into a spark plug wire, or, in Coil-On-Plug (COP) systems, the coil sits directly on top of the spark plug, depending on the type of coil you have. A single coil supplies voltage to the distributor in older vehicles with a distributor. Whereas other automobiles use a single coil for each spark plug wire, DIS, or wasted spark systems, use what is commonly refer to as a “coil pack” to send voltage to each spark plug wire. COP is now incorporate into most recent vehicles.

  • A basic tool kit to remove coils
  • A multimeter or an ohmmeter
  • Spark plug or ignition tester

Ignition coils can fail in one of two ways: either completely and without any output, or intermittently, with the coil becoming weak and having low output or working occasionally but not always. Intermittent issues are therefore more challenging to diagnose. Because you must remove the coils before testing them, you should conduct your initial diagnosis by looking for typical symptoms of a bad ignition coil. If you find that the symptoms don’t match, you can save time this way. The signs of a faulty ignition coil are as follows:

  • Misfires – Check Engine Light: The first and most prevalent symptom is typically misfiring, which in the majority of modern cars will trigger the Check Engine Light. The misfire will either occur randomly or on a specific cylinder. In most cases, specific-cylinder misfires are simpler to identify than random-cylinder ones. An ignition coil or coils may be to blame if the vehicle is jerky, stumbles, or lacks acceleration and a misfire is indicate by a check engine light code.
  • Rough Idling or Hesitation Under Load: As previously mentioned, most ignition issues that result in misfires also result in a rough or bad idle, but when a car (typically an older model) lacks a Check Engine light or the ability to detect a misfire, a rough idle or constant stalling may be an indication of a bad ignition coil or an overheating coil, while hesitation under load may also be an indication of a weak coil.
  • No-Start Situation: Some people check the ignition coil first when their car won’t start, especially if it’s an older model. Even on newer cars, a coil can fail between the last run cycle and the subsequent start-up, albeit this is frequently not the cause since there are many other ignition system components. In certain situations, the car might have operated smoothly, but on the subsequent start, it either won’t start or runs badly. The ignition coil or coils could be questionable in either case.
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Testing Ignition Coil

Prior to testing ignition coils, it’s important to understand a few critical points. One is that there are numerous testing techniques, some low-tech and some high-tech, and we shall discuss them all.

Again, it’s crucial to keep in mind that intermittent coil failures are more challenging to identify. A processor, or “Ignition Module,” is use by various ignition systems, most notably DIS or “wasted spark” coil pack systems and a number of COP systems, to appropriately power and deliver signals to the ignition coils. While these problems may give the impression that the coil isn’t functioning, the issue is with the ignition module. We’ll highlight a few different ways to diagnose coil problems below.

How to Test Ignition Coil?

If you’re experiencing problems with your car’s ignition system, it may be time to diagnose and repair the problem. In this blog post, we’ll discuss the basics of testing your ignition coil and how to do it safely and correctly. We will also provide instructions on how to replace an ignition coil if it’s broken or damaged. By following these simple steps, you can get your car back up and running quickly and without any hassle.


The easiest and quickest way to start diagnosing a car is to replace the ignition coil with a different well-known unit. This method is great for cars with single coils, multi-packs, or Coil-on-Plugs. As previously stated, a misfire typically occurs on a particular cylinder in these situations. Let’s say that on a vehicle with Coil-on-Plug packs, cylinder 3 misfires. Simply swap the coil from cylinder 3 for the one from cylinder 6 by removing another coil. You can now clear your engine codes with a code reader. If not, write down the engine code you used.

Now, start the car and drive for a while. As the defective coil from #3 was moved to #6, you will now see an engine code for “Misfire – Cylinder 6” if the ignition coil was indeed defective. Pull the #6 coil you just moved and replace as your next step. If you swap these coils and still experience a misfire on cylinder 3 but it does not move. You know that the coil is not the problem. You either have a problem with the ignition module (some COP units use a module, others do not). A problem with the connector or lead of the coil, a problem with the spark plug, a problem with the fuel injector, or a mechanical problem with that cylinder’s internal engine.

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General Inspection

On any coil – look it that over carefully for signs of cracks, burns, melting, or leakage in older canister coils. This often points to a problem on its own, so check carefully.

Test the Windings with a Multimeter

It has long been common practice to measure the Ohm’s resistance of coils using a multimeter. Although it functions somewhat, a significant drawback is that you cannot simulate load or evaluate the coil while it is in use. As a result, weak coils that are not performing may still pass this test but still be terrible.

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Nonetheless, checking the coil’s windings for appropriate resistance can aid in identifying potential issues. The primary winding and secondary winding are two distinct coils that are wrap around one another to make up an ignition coil.

Check your vehicle’s specific repair manual, or online to find out what the correct resistance reading should be for both the primary and secondary windings. Both must be tested.

  • To test the primary and secondary windings, attach the positive and negative leads of the multimeter to the appropriate terminals as directed. Depending on the coil’s design, different coils will have various touch points. You should be able to find out exactly where and which pins to touch off to in your repair manual or online.
  • Check the reading on the multimeter and compare it to the resistance specifications for both that primary and secondary windings.

You’ll need to swap out the ignition coil if the reading is outside the typical resistance range. A zero indicates an internal coil short. The coil is open if the reading is abnormally high. Make sure your leads are place correctly by double-checking their positioning.

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Spark Test or Active Analyis

Keep in mind that when a coil fails, it frequently becomes weak. It still gives off spark and may occasionally continue to drive smoothly, but it can frequently misfire when the vehicle is loaded or moving quickly. In other instances, the coil completely fails and ceases to function. Without replacing parts and hoping, sometimes the only way to confirm what is going on is to actually perform an on-vehicle spark or output test. It is important to note that the ignition coil swap described in step 1 is typically the fastest and easiest way to determine if you have a coil issue with any Coil-on-Plug vehicle (COP).

There are a variety of methods and tools that can be utilized to carry out a spark test or active analysis of the coil’s operation while it is mounted on the vehicle. Keep in mind that with any of these. You will frequently be testing the output of the coil while the vehicle is running; therefore. You should read any spark test procedures in a repair manual or an online tutorial. Simply pulling the coil wires off while the vehicle is running can cause shock or serious injury. You can also investigate the “power balance test” to pinpoint the location of the cylinder problem. We’ll talk about a few different types of coils and the basics of how to test them, as well as the tools you need to do so:

  • It may be useful to use an inline ignition tester like OEM 25227. This device provides a window to view an active spark and runs inline with numerous spark plug wires and/or coils.
  • In its stead, an ignition spark tester like OEM 25069 is ground to the engine and can quickly demonstrate whether a certain wire or coil is producing spark.
  • Inductive technology is used in a number of new technological products. Such as COPs (coil on plug tests), to determine whether a coil is firing properly without ever removing the coil. Several tiny, reasonably priced oscilloscopes are also available. And you can get tutorials on how to use them online and on YouTube. With these, you can pinpoint a poor coil output without ever having to remove the coil or wires.

Now, let’s cover different types of coils, and diagnostic methods to pinpoint an issue.

  • Coil-on-Plug (COP): These coils are easy to spot because they are bolted to the engine’s valve or cam cover and have a rubber boot that connects directly to the spark plug. Switching the coil with a neighboring coil to see if the misfire moves to a different cylinder is the easiest and best way to identify a problem with these coils. You can also remove the coil, plug it back in. And use an ignition spark tester like OEM 25069 to see if the coil is firing if you think it is dead. A multimeter can also be use to measure resistance. Similar to the LS motors found in Chevy and GMC trucks. Individual coils for each cylinder can adhere to this procedure as well.
  • DIS (Wasted Spark) Coil Packs: For well over two decades, the majority of ignition systems utilized coil packs. Spark plug wires are connected to tower terminals on these units. Which make use of either a single pack or a series of packs. When one cylinder fires on the compression stroke and one is wasted on the exhaust stroke of another. They are known as “Wasted Spark” ignitions because they frequently have terminal pairs that fire simultaneously. An Ignition Module, which can fail, typically powers and controls them. A single terminal running a single cylinder or a pair of terminals can fail on the pack at any given time. You can also use the #1 “swap” method to move the coil pack to a neighboring position and see if the misfire moves to those cylinders if your system is made up of several of the same packs (like a V6 engine with three packs, each with two terminals). You can also test with an OEM 25227 ignition tester. In this instance, it’s a good idea to compare the spark’s intensity to that of a cylinder you know is working properly to one you think might be bad. If you notice that the spark is significantly weaker, the coil may be defective and should be replaced. The windings on these coils can also be tested using a multimeter. But because there are multiple terminals and towers to test, these methods can get complicated.
  • Traditional Single Coil: Since the 1920s, the single-terminal “canister” coil has existed in one form or another. Millions of vintage vehicles still use distributors, even though they are no longer use in vehicles today. A multimeter test for resistance on these coils is a good place to start. As is an inline spark test to make sure the coil is working properly. Keep in mind that your resistance test won’t always give you the right answer because many of these coils can have intermittent issues, especially when they overheat or vibrate. Fortunately, most of these coils aren’t too expensive. And if all of your testing hasn’t found a solution to a persistent intermittent issue. Replacing the coil with a well-known model might be the best option.
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Thank you for reading our article on how to test ignition coil. In this article, we will provide you with a comprehensive guide that will help you diagnose and fix your ignition coil. We will also provide you with a conclusion of this article, in which we’ll outline the most important points that you need to know about testing your ignition coil. So if you’re having trouble starting your car, or just want to be sure that your ignition coil is in good condition, read on to learn everything you need to know.

Coil or the ignition system diagnosis might occasionally be challenging. It can occasionally be expensive and ineffective to just replace out the parts to diagnose the issue. Professional businesses frequently have a variety of pricey, cutting-edge equipment to assist with these operations. And frequently allowing them the chance to identify the problem ends up being more affordable and quicker. Locate a nearby Preferred Shop that can assist you with this.

Frequently Asked Questions

How to Test an Ignition coil?

You may remove the coil, plug it in, and use an ignition spark tester like OEM 25069 to determine if the coil is firing if you believe it’s dead. Resistance can also be measured using a multimeter.

How do you check an ignition coil with a multimeter?

You will need to connect the multimeter leads to the coil terminals in order to test a coil with a multimeter. Set the multimeter to resistance mode and measure the coil’s resistance once you’ve established a connection.

What is the best way to test an ignition coil?

Ignition coils have two circuits that require checking; primary and secondary circuits. Connect the multimeter to the negative and positive terminals of the ignition coil to get a primary circuit reading. If the multimeter shows a reading of 0 ohms, the ignition coil has shorted and needs replacing.

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