As you may already know, your Honda with a 2.4L 4 cylinder has four individual ignition coils. These ignition coils are commonly known as Coil On Plug (COP) ignition coils.
What you may not know is that testing them is pretty easy. Furthermore, you don't need any expensive diagnostic equipment. In this tutorial, I'll show you how to do it in a detailed step-by-step fashion. You'll be able to say that “Yes, the COP coil is bad” or “No, the COP coil is NOT bad”.
Let's get started with some basic info in the next section.
NOTE: This tutorial applies to the 2003, 2004, 2005, and 2006 2.4L Honda Accord And Element.
You can find this tutorial in Spanish here: Cómo Probar Las Bobinas De Encendido (2003-2006 2.4L Honda Accord) (at: autotecnico-online.com).
Symptoms Of A Bad COP Ignition Coil
When one or more COP ignition coil fails, the engine in your Honda will experience a misfire condition. This translates into an engine that's not running on all cylinders.
The most obvious symptom of bad cop ignition coil, is a miss at idle and when you accelerate your Honda down the road.
You're also gonna' see the check engine light (CEL) shining nice and bright on your instrument cluster and one (or several) of the following:
- Diagnostic trouble codes:
- P0300: Random Cylinder Misfire.
- P0301: Cylinder #1 Misfire.
- P0302: Cylinder #2 Misfire.
- P0303: Cylinder #3 Misfire.
- P0304: Cylinder #4 Misfire.
- Rough idle.
- Smell of raw gasoline coming out of the tailpipe.
- Bad gas mileage.
- Won't pass the emissions test.
- Extended cranking time (hard start).
- If more than one ignition coil is bad, your Honda won't start.
If your vehicle is experiencing any of the above symptoms, chances are that you do have a bad COP coil on your hands. Let's take a look at some of the basic tools you'll need to diagnose and repair this yourself.
What Tools Do I Need To Test The COP Coils
The most important tool that you're gonna' need, to test the ignition coils for spark, is a spark tester.
A lot of folks check the COP ignition coils for spark by simply pulling the ignition coil off of the spark plug (while the car is running)and hearing for the audible clicking sound the spark makes. But, this is the worst way to check for spark. Why? Because you run the risk of damaging the ignition coil you're testing in this way.
I'm gonna' recommend one that is the most effective (and the most inexpensive) out there: the HEI spark tester (OTC 6589 Electronic Ignition Spark Tester).
From personal experience (I work full-time as an automotive tech) I can tell you that the HEI spark tester is a must-have tool. You don't need to interpret the color of the spark or the weakness of it. If the HEI spark tester sparks then you can conclude that the ignition coil is good.
- An HEI spark tester.
- To find out more about this inexpensive yet accurate spark tester, go here: The HEI Spark Tester (The Best Spark Tester On The Market) (this article at: easyautodiagnostics.com).
- If you need to buy one, you can buy it here: OTC 6589 Electronic Ignition Spark Tester
- Scan tool.
- A scan tool is not needed to check the COP coils with the info I'm presenting in this tutorial but it does come in handy to retrieve the misfire DTC (diagnostic trouble code).
- Don't have one? Check out my recommendation: Actron CP9580 Scan Tool Review.
- Wire piercing probe.
- Although this tool is not an absolute must, if you do buy one, you'll realize just how easy it makes testing the voltages inside the wires.
- If you need to see what this tool looks like, you can see it here: Wire Piercing Probe.
How Does The COP Coil Work?
Although it's not absolutely necessary to know how the ignition coils work on your Honda vehicle, I've included a brief description of how they work (for those of you who love to read the how and why of stuff).
In a nutshell, the COP ignition coil's job is to create and deliver spark to the spark plug.
Having an individual ignition coil per cylinder allows for a more maintenance free ignition system, since you have less moving parts that may wear out and that eventually need to be replaced, like:
- A mechanical distributor assembly.
- Distributor cap.
- Distributor rotor.
- Spark plug wires.
Now in case you're really curious about how it works, below is a very brief description of the whole process:
- When you turn the key and crank the engine, power and Ground are supplied to 2 of the 3 wires sticking out of the COP ignition coil's electrical connector.
- The PCM (Powertrain Control Module = Fuel Injection Computer) gets the crankshaft position signal from the crank sensor.
- The PCM now activates each COP ignition coil.
- This activation signal (Triggering signal) is supplied to the third remaining wire of the COP ignition coil's electrical connector.
- This Triggering signal activates an ignition module (also known as the power transistor) within the ignition coil
- The ignition module, in turn, starts to switch the ignition coil 12 Volts ON and OFF (by interrupting the coil's Ground circuit). Remember, all this is happening inside the ignition coil.
- It's the switching ON and OFF of the primary current (the fancy name for 12 Volts) that causes the COP coil to spark.
- With all 3 signals supplied (power, ground, and the triggering signal), the ignition coil now starts to spark.
- With fuel being injected, the engine in your Honda comes to life.
OK, with this brief overview of how the COP ignition coil works on your 2.4L equipped Honda, let's turn the page and get testing.