How To Test The Ford 4.6L, 5.4L Coil-On-Plug Ignition Coils

TEST 2: Checking For Battery Power

OK, you're here because in TEST 1 you got a no-spark result from one of several ignition coils. The next step is to verify that that ignition coil or coils are receiving power.

The power the ignition coils receive is in the form of 10 to 12 Volts DC. In this section, we'll check for the presence of this voltage using a multimeter.

NOTE: Be careful not to damage the female terminal (of the connector) with the multimeter test leads, or you'll need to replace the connector.

Let's get testing:

1. 1

   Disconnect the ignition coil that did not spark from its 2-wire connector.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

   Connect the black multimeter test lead to the battery negative (-) terminal.

4. 4

   Gently probe the female terminal of the connector that connects to the wire labeled with the number 2 (see photo above) with the red multimeter test lead.

5. 5

   Have your helper turn the key to the ON position.

6. 6

   You should see 10-12 Volts on your multimeter.

Let's take a look at what your test results mean:

CASE 1: The multimeter registered 10-12 Volts (or the test light lit up). This test result tells you that the power circuit is OK and is delivering voltage.

The next step is to test the Switching signal circuit, go to: TEST 3: Checking For The Switching Signal.

CASE 2: The multimeter DID NOT register 10-12 Volts (or the test light DID NOT light up). This test result confirms that the power circuit has a problem.

This result eliminates the COP ignition coil as the source of the misfire condition. The power circuit is shared by all of the COP ignition coils.

TEST 3: Checking For The Switching Signal

OK, you're here because you have confirmed that the ignition coil is not sparking and that 12 Volts are present. The next step is to verify that the ignition coil's is receiving the switching signal from the fuel injection computer. We'll be using an LED light.

Testing for the Switching signal can be done with the ignition coil connected or disconnected to its connector. The method I recommend to use is with it connected to its connector and with a wire-piercing probe (you can see what this tool looks like here: Wire-Piercing Probe).

The other method is to unplug the ignition coil connector and insert the male spade terminals of the LED into the connector's female terminals. If you go this route, keep the following in mind:

• The red wire of LED goes into the female terminal that connects to the red wire of the connector. This wire is labeled withe the number 2 in the photo above.
• The black wire of the LED goes into the female terminal of the wire labeled with the number 1.

NOTE: If you do insert the LED wires into the terminals, make sure that whatever size terminal you insert into them does not open them up. If this happens, you are going to create yourself a major headache.

These are the test steps:

1. 1

   Connect the black lead of the LED light to the wire labeled with the number 1.

2. 2

   Connect the red lead of the LED the battery positive (+) terminal.

3. 3

   Have your helper crank up the engine as you observe the LED light.

4. 4

   The LED light should flash ON and OFF the whole time the engine is cranking and running.

Let's take a look at what your test results mean:

CASE 1: The LED light flashed ON and OFF. This test result confirms that the Switching signal is present. This result also indicates that the Coil-On-Plug ignition coil on your Ford car or truck is bad and needs to be replaced.

CASE 2: The LED light DID NOT flash ON and OFF. Re-check all of your connections and repeat the test again.

If still no flashing ON and OFF, then this results eliminates the ignition coil as the source of the no-spark condition/misfire, since without the Switching signal the ignition coil will not work.

There are several possible causes for this that I've seen time and time again with the most common being: An open-circuit problem in the wire that feeds the Switching signal between the fuel injection computer and the COP ignition coil. The second most common: A fried fuel injection computer. Although testing these two conditions are beyond the scope of this article, you have at least eliminated the ignition coil itself as the cause of the problem.

What's The Switching Signal: The ‘Switching Signal’ really isn't a physical signal, the term is used to describe how the fuel injection computer opens and closes the Primary Current's (flowing thru' each ignition coil) path to Ground. It's this action that makes the ignition coil fire off spark.

This ‘ON/OFF’ action can be measured so many different ways and with different types of diagnostic equipment. Using a LED is a simple and inexpensive way of verifying the existence of this signal.

Why is the fuel injection computer providing this signal and not an ignition control module? Well, it's because the ignition control module function is inside the computer itself on this type of Ford Coil-On-Plug ignition system. Therefore, one of the two wires in each of the ignition coil's connector goes straight the fuel injection computer, although they do not share the same circuit.