How To Test The Ignition Coils (2003-2007 3.0L V6 Honda Accord)

In this step-by-step tutorial, I'll show you how to test the Coil-On-Plug (COP) ignition coils using a spark tester.

You'll learn how to check for spark, verify power and Ground, and confirm that the PCM is sending the activation signal.

So, if your 2003–2007 3.0L V6 Honda Accord is misfiring and you're suspecting a bad ignition coil, you've come to the right place.

APPLIES TO: This tutorial applies to the following vehicles:

• 3.0L V6 Honda Accord: 2003, 2004, 2005, 2006, 2007.

IGNITION SYSTEM WIRING DIAGRAM: The following wiring diagram complements the info in this tutorial.

• Ignition Coil Circuit Wiring Diagram (2003-2007 3.0L V6 Honda Accord).

Symptoms Of A Bad Ignition Coil

A bad ignition coil will cause the cylinder it supplies spark to misfire. When that happens, you'll feel the engine shake or rough idle, especially when stopped at a light or in gear. On the road, you might notice hesitation or a lack of power when accelerating.

Most of the time, this kind of misfire will trigger a check engine light. If you scan for trouble codes, you'll see one of these:

• P0300: Random Cylinder Misfire.
• P0301: Cylinder #1 Misfire.
• P0302: Cylinder #2 Misfire.
• P0303: Cylinder #3 Misfire.
• P0304: Cylinder #4 Misfire.
• P0305: Cylinder #5 Misfire.
• P0306: Cylinder #6 Misfire.

Other signs of a bad coil include:

• Hard starts or a long crank time.
• Bad gas mileage, especially if the misfire is happening constantly.
• Raw fuel smell from the exhaust if the cylinder isn't firing and the injector is still spraying fuel.
• Intermittent rough running, where the misfire comes and goes —making it trickier to catch.

For a more in-depth look at how to troubleshoot a cylinder misfire, this tutorial digs deeper into the most common causes, how to test them and resolve them:

• How To Test a Misfire Condition and Misfire Codes (1998-2007 3.0L V6 Honda Accord).

TEST 1: Testing For Spark

Before we begin with our spark tests, I want to tell you that you don't have to test all six ignition coils unless you want to.

You can just test the one you suspect is causing a cylinder misfire (if you've identified the "dead" cylinder with a misfire trouble code). The test steps and result interpretations below take all this into account, so you're covered either way.

One more thing, to get an accurate test result, you'll need a dedicated spark tester —preferably the HEI type. Using anything else, like a regular spark plug, just won't give you reliable results and could lead to replacing a good coil for no reason. Also, don't try the old trick of pulling the coil off while the engine's running— that can fry the coil and give you a whole new headache.

If you need to purchase a spark tester, this is the one I have always used and recommend:

• OTC 6589 Electronic Ignition Spark Tester (Amazon affiliate link)

MISFIRE DIAGNOSTICS: If you need a more in-depth tutorial on how to troubleshoot a cylinder misfire, see this tutorial: How To Test a Misfire Condition and Misfire Codes (1998-2007 3.0L V6 Honda Accord).

Let's get this show on the road:

1. 1

   Remove the Coil-On-Plug ignition coil you want to test.

2. 2

   Connect your spark tester to the ignition coil.

3. 3

   Ground the spark tester to the battery's negative (-) terminal.
   
   I like to use a jumper cable to make the connection quick and easy.

4. 4

   Have a helper crank the engine while you watch the spark tester.

5. 5

   You're gonna see one of two things: either the tester sparks or it doesn't.

6. 6

   Once done, disconnect the spark tester and reinstall the ignition coil.

7. 7

   If needed, repeat this process for any other ignition coil(s) you need to test.

This is what your results mean:

CASE 1: You tested all six coils and all produced spark. That's good news —your coils are working fine. The misfire is being caused by something else.

CASE 2: One or more ignition coils did not spark. The ones that failed to spark are likely faulty.

But before replacing any of them —you'll need to confirm that those coils are actually getting power, Ground, and and activation signal. Head over to: TEST 2: Making Sure The Ignition Coil Is Getting 12 Volts.

CASE 3: None of the coils fired off spark. It's almost unheard of for all six coils to fail at once. That usually points to a deeper issue, like:

• A failed camshaft or crankshaft position sensor.
• A bad ignition switch.
• A blown fuse.

TEST 2: Making Sure The Ignition Coil Is Getting 12 Volts

If TEST 1 showed that one or more coils aren't firing off spark, then the next logical step is to check if those coils are even getting power in the first place.

Each Coil-On-Plug ignition coil needs 10 to 12 Volts DC to function, and if that voltage is missing —well, the coil isn't gonna do its job.

The wire that supplies power is marked with the number 1 in the photo above. That's the one we'll be testing with a multimeter. Be careful when probing the connector though —the metal inside the female terminal can get damaged if you're not gentle or use the wrong type of probe.

Alright, let's get to it:

1. 1

   Unplug the ignition coil from its electrical connector.

2. 2

   Set your multimeter to Volts DC mode.

3. 3

   Touch the red multimeter lead to the terminal labeled "1" in the connector. (Use a probe tip that fits properly —don't force it.)

4. 4

   Touch the black multimeter lead to the battery's negative (-) terminal.

5. 5

   Have your helper turn the key to the ON position (engine off).

6. 6

   Look at the reading on your multimeter. You should see somewhere between 10 and 12 Volts.

Let's see what this is pointing to:

CASE 1: The multimeter shows 10–12 Volts. This confirms that the ignition coil is receiving the power it needs to operate.

That means you can move on to the next step: TEST 3: Making Sure The Ignition Coil Is Getting Ground.

CASE 2: There's no voltage —the multimeter shows 0 Volts. This tells you the ignition coil isn't receiving power. And without power, it's not going to fire spark no matter what. In this situation, the coil itself is most likely fine— the real issue is a missing voltage supply.

The usual suspects here include:

• A damaged or corroded ignition coil connector.
• An open-circuit problem in the power wire between the coil and the engine wiring harness.

TEST 3: Making Sure The Ignition Coil Is Getting Ground

Now that you've confirmed that the non-sparking ignition coil is getting power (10–12 Volts), the next thing to check is if it's getting a proper Ground. Without a solid Ground, the coil won't function —even if it has voltage and a trigger signal.

The Ground for each coil comes from the vehicle's chassis and is always available —whether the key is ON or OFF. The Ground wire is the one that connects to terminal 2 of the ignition coil's 3-wire connector.

The wire that connects to terminal 2 is the black (BLK) wire of the connector.

To check for Ground, we'll do a quick multimeter voltage test.

Alright, let's begin:

1. 1

   Disconnect the ignition coil from its electrical connector.

2. 2

   Set your multimeter to Volts DC mode.

3. 3

   Connect the red multimeter lead to the battery positive (+) terminal.

4. 4

   Probe terminal 2 of the ignition coil connector with the black multimeter lead. This is the one that connects to the black (BLK) wire.

5. 5

   You should see around 10–12 Volts if Ground is present.

Here's what your test result means:

CASE 1: You saw 10–12 Volts on your multimeter. That means the ignition coil's Ground circuit is good —no issues there.

The next thing to check is the triggering signal from the PCM. Go to: TEST 4: Checking The Coil's Activation Signal.

CASE 2: The multimeter did not register voltage (0 Volts). This indicates the coil is missing its Ground connection. And without Ground, it can't function —even if it's getting power and a trigger pulse.

The most likely causes are:

• An open-circuit problem in the wire somewhere between the ignition coil connector and chassis Ground.
• Corrosion or damage at the Ground splice or terminal.

TEST 4: Checking The Coil's Activation Signal

Up to this point, you've verified:

• The ignition coil isn't firing spark (TEST 1).
• It's getting battery voltage (10–12 Volts) at the power feed wire (TEST 2).
• It has a good Ground connection at terminal 2 (TEST 3).

The final piece of the puzzle is confirming whether or not the coil is receiving its activation signal from the PCM (Powertrain Control Module).

This signal is delivered through the wire that connects to terminal 1 of the ignition coil's 3-wire connector. Each coil has its own signal wire, and the wire color is gonna differ between them. If you need to know which color corresponds to which cylinder, take a look at this wiring diagram:

• Ignition Coil Circuit Wiring Diagram (2003–2007 3.0L V6 Honda Accord)

You've got two options for testing the signal:

• Use a multimeter with a Hertz (Hz) frequency function (recommended).
• Or, skip the multimeter and do a simple coil swap. If you'd rather go that route, jump over to: TEST 5: Swapping The Ignition Coil.

Don't have a multimeter with Hz mode? This is the one I use all the time and fully recommend:

• Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter (Amazon affiliate link).

Now, one important detail: You'll perform this test with the ignition coil plugged in. I recommend using a back probe or a wire-piercing probe to safely access the signal wire. If you're not familiar with those tools, see this link:

• Wire-Piercing Probe

Here's how to check for the activation signal:

1. 1

   Switch your multimeter to the Hertz (Hz) setting.

2. 2

   Reconnect the ignition coil to its harness connector.

3. 3

   Connect the the black multimeter lead to the ignition coil's signal wire. Use wither a back probe or a wire piercing probe.
   
   NOTE: The ignition coil activation signal wire will connect to terminal 1 of the 3-wire connector. This will differ in color between ignition coils.

4. 4

   Touch the red multimeter lead to the battery's positive (+) terminal.

5. 5

   Have a helper crank and start the engine.

6. 6

   You should see a fluctuating reading between 30 and 60 Hz on your meter.

Let's see what your test result is telling us:

CASE 1: The multimeter displayed 30 to 60 Hertz (Hz) while the engine was cranking or running. This confirms that the PCM is sending the coil the proper trigger signal. If you've also confirmed:

• No spark from the coil (TEST 1),
• Power at the connector (TEST 2),
• Good Ground connection (TEST 3),
• And now, a valid trigger signal (this test),

Then you can confidently say the ignition coil is bad and needs to be replaced.

These are the replacement ignition coils from two known automotive brands I use, trust, and recommend:

• Standard Motor Products UF400T Ignition Coil (Amazon affiliate link)
• Delphi GN10168 Ignition Coil (Amazon affiliate link)

Using these links helps support the site at no extra cost to you —and I appreciate it more than you know.

CASE 2: The multimeter did not show any Hertz reading during cranking or running. Double-check your test setup and try again.

If you're still not seeing any signal, that tells you the PCM isn't triggering the coil —and that's why there's no spark.

This eliminates the ignition coil itself as the problem. The most likely cause of this missing signal is an issue with the connector or an open-circuit issue in the signal wire between the connector and the PCM. Your next step is to find out why this signal is missing and restore it to the circuit.

TEST 5: Swapping The Ignition Coil

If you don't have a multimeter with a Hertz function, you can still verify the presence of the coil's activation signal by doing a simple coil swap. The idea here is to take a known-good ignition coil —one that you've confirmed sparks— and plug it into the connector of the one that isn't sparking.

If the known-good coil fires when connected to the non-sparking coil's harness connector, then you know the activation signal is present —and that the original coil is the one at fault.

Let's walk through the steps:

1. 1

   Disconnect and remove the ignition coil that isn't producing spark.

2. 2

   Pick another coil that you know is firing spark and remove it from its location.
   
   If you're unsure, you can test it again using your HEI spark tester.

3. 3

   Plug the working ignition coil into the electrical connector that belongs to the non-sparking coil.
   
   Hook up your spark tester to the known-good coil, and Ground the spark tester to the battery's negative (-) post using a jumper cable.

4. 4

   Take the non-sparking coil and bolt it into the spot where the good coil came from. (We're just swapping their locations so nothing is left disconnected.)

5. 5

   Once everything is set up, have your helper crank the engine.

6. 6

   Watch the spark tester. The good coil should spark if the signal is present.

Let's see what this result is pointing to:

CASE 1: You saw spark from the good ignition coil. That confirms the activation signal is making it to the connector. If you've also verified:

• No spark from the original coil (TEST 1),
• Voltage is present (TEST 2),
• Ground is good (TEST 3),
• And now the connector is confirmed to be sending a signal (this test),

Then the original coil is definitely bad and should be replaced.

These are the replacement ignition coils from two known automotive brands I use, trust, and recommend:

• Standard Motor Products UF400T Ignition Coil (Amazon affiliate link)
• Delphi GN10168 Ignition Coil (Amazon affiliate link)

Using these links helps support the site at no extra cost to you —and I appreciate it more than you know.

CASE 2: You didn't get any spark from the good coil. This tells you the connector isn't sending a trigger signal and that rules out the non-sparking ignition coil itself as the cause of the misfire— it simply isn't being activated.

The most likely cause of this missing signal is an issue with the connector or an open-circuit issue in the signal wire between the connector and the PCM. Your next step is to find out why this signal is missing and restore it to the circuit.

More 3.0L V6 Honda Accord Diagnostic Tutorials

I've written quite a few how-to guides for the 3.0L V6 Honda Accord, written with both DIYers and experienced techs in mind. You can find them all in this index:

• 3.0L V6 Honda Accord Index Of Articles.

Here's a quick peek at some of the step-by-step tutorials you'll find there:

• How To Troubleshoot A No Start (1998-2007 3.0L V6 Honda Accord).
• How To Test For A Broken Timing Belt (1998-2007 3.0L V6 Honda Accord).
• How To Test a Misfire Condition and Misfire Codes (3.0L V6 Honda Accord).
• How To Test Engine Compression (1998-2007 3.0L V6 Honda Accord).