IGNITION COIL TEST 3: Checking For 12 Volts

How To Test The Ignition Coil -No Start Tests (Chrysler 3.9L, 5.2L, 5.9L)

So far, in troubleshooting the ignition coil, you have:

1. Made sure that there's no spark from the ignition coil wire (TEST 1).

2. You have tested for spark directly on the ignition coil and go a no spark test result.

The next couple of tests are to see if the ignition coil is getting fed with power (12 Volts) and the switching signal.

In this test step, you'll check for these 12 Volts either using a multimeter or a 12 V DC test light.

Alright, this is what you'll need to do:

  1. 1

    With your multimeter still in Volts DC mode from the previous test.

  2. 2

    Probe the wire labeled with the number 2 in the image viewer, with the RED multimeter lead.

  3. 3

    Now ground the multimeter's BLACK test lead on the battery's negative (-) post.

  4. 4

    Crank the engine. This is important, because the ignition coil will only get power when the engine is either cranking or running.

  5. 5

    Your multimeter should show you either: 1.) 12 Volts DC or 2.) 0 Volts.

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

CASE 1: The multimeter registered 12 Volts: This is the correct result and tells you that the ignition coil is getting battery power (12 Volts).

The next step is to check that the ignition coil is getting a switching signal from the powertrain Control Module (PCM). Go to IGNITION COIL TEST 4.

CASE 2: The multimeter DID NOT register 12 Volts: double check your multimeter connections and repeat the test... if your multimeter results still do not indicate 12 Volts, then ignition coil is not fried and not the cause of the no spark No Start problem, since without power, it won't work.

The two most likely causes for this missing voltage are: 1.) The Auto Shut Down (ASD) relay is BAD or 2.) the crank sensor is BAD.

Although it's beyond the scope of this article to find the cause of these missing 12 Volts, resolving this issue will solve the no spark No Start issue.

IGNITION COIL TEST 4: Verifying The Switching Signal

How To Test The Ignition Coil -No Start Tests (Chrysler 3.9L, 5.2L, 5.9L)

In the previous test you confirmed that the ignition coil is being supplied with power (12 Volts DC).

Now, you need to see if the ignition coil is getting an activation signal, called the switching signal, from the PCM.

This switching signal from the PCM is what actually activates the ignition coil to fire off spark.

This test is accomplished using a 12 Volt test light and is done while cranking the engine on your 3.9L, 5.2L, or 5.9L Dodge pick up (or van or SUV).

Alright, this is what you'll need to do:

  1. 1

    Reconnect the high tension wire to the ignition coil and the distributor cap, if you haven't done so.

  2. 2

    Probe the wire labeled with the number 1 in the image viewer with the metallic tip of the 12 Volt test light.

    Connect the alligator clip (of the 12 V test light) to the positive (+) battery terminal. The ignition coil can be connected to its electrical connector or not.

  3. 3

    When ready, have your helper crank the engine while you observe and hold the test light in place.

  4. 4

    Your 12 Volt test light will either:

    1.) Flash On and Off the whole time the engine is cranking.

    2.) No flashing On or Off.

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


CASE 1: The test light flashed On and Off: This is means that the power Control Module (fuel injection computer) is activating the ignition coil and since the ignition coil is not sparking... the ignition coil is BAD. Replace the ignition coil.

Here's why: If the ignition coil is getting power (12 Volts) and is getting the switching signal, it HAS TO SPARK, since it isn't, this tells you that it's fried.

If you'd like to save a few bucks on the ignition coil, take a look at the section: Where To Buy The Ignition Coil and Save.

CASE 2: The test light DID NOT flash On and Off: this test result exonerates the ignition coil, since without this switching signal, it won't spark.

The most likely causes of this missing switching signal are: a bad crank sensor, an open or a short in the wiring between the PCM and the ignition coil's connector, or the PCM (Powertrain Control Module = fuel injection computer) is BAD (although this is a rare thing).

Altho' it's beyond the scope of this article to test the wiring or the PCM, you have at least eliminated the ignition coil as BAD.

To test the crank sensor, I suggest taking a look at the following tutorials:

  1. How To Test The Crank Sensor (1994-1996 3.9L, 5.2L, 5.9L Chrysler).
  2. How To Test The Crank Sensor (1997-2001 3.9L, 5.2L, 5.9L Chrysler).