How To Test The Power Transistor 2.4L Nissan Altima (1997-2001)

How To Test The Power Transistor 2.4L Nissan Altima (1997-2001)

If the igniter (which is called the power transistor by Nissan) on your 2.4L Nissan Altima goes bad, the is not gonna' start. More specifically, it'll crank but not start due to a lack of spark.

This tutorial will help you to test the power transistor (also known as the ignition control module and igniter) that's located inside the distributor assembly on your 1997, 1998, 1999, 2000, or 2001 2.4L Nissan Altima.

The power transistor test I'm gonna' show you is an on-car test and is done without a scan tool or any other expensive diagnostic tool.

In Spanish You can find this tutorial in Spanish here: Cómo Probar El Módulo De Encendido (1997-2001 2.4L Nissan Altima) (at:

Important Tips And Suggestions

TIP 1: Since this is an on-car test of the power transistor (ignition control module) and is tested in action, you'll be working around a cranking engine. So you have to be alert and careful.

TIP 2: The battery in your 2.4L Nissan Altima must be fully charged, since you'll be cranking the engine for some of the tests.

TIP 3: You need to test for spark first, before attempting this power transistor test, because if you have spark, the power transistor is good and doing its job.

I recommend that you start your power transistor (igniter) diagnostic by first doing the ignition coil test found here: 2.4L Nissan Ignition Coil Test (97-01).

TIP 4: The igniter (power transistor) is part of the camshaft position sensor and is located inside the distributor.

TIP 5: If the igniter (power transistor) is fried, you'll have to replace the entire distributor, since it's not sold separately.

How Does The Power Transistor (Igniter) Work?

How To Test The Power Transistor 2.4L Nissan Altima (1997-2001)

What's gonna' help you to see the 'why and how' of the power transistor tests in this tutorial, is to understand how it works.

In a nutshell, this is what happens:

  1. The power transistor is located inside the distributor and is part of the camshaft position sensor assembly.
  2. The camshaft position sensor assembly is really a crankshaft position sensor, since the fuel injection computer uses this sensor to control the creation of spark thru' the power transistor and ignition coil.
  3. Now, when you turn the key and crank the engine (to start it), the camshaft position sensor/power transistor get power thru' the wire labeled with the number 5 (see photo above).
  4. As the engine turns, the camshaft position sensor assembly starts to create two specific position signals that it sends directly to the computer. When the computer gets these two signals, it does its little song and dance and shoots a Triggering signal to the power transistor.
    • This Triggering signal can be checked with an LED light (which you'll do in TEST 2).
  5. When the power transistor gets the Triggering signal from the fuel injection computer, it now starts to switch the ignition coil's power ON and OFF. This ON/OFF action is what makes the ignition coil spark and is referred to as the Switching signal.
    • This Switching signal can be checked with an LED light (which you'll do in TEST 3).

TEST 1: Making Sure The Power Transistor Is Getting Power

How To Test The Power Transistor 2.4L Nissan Altima (1997-2001)

The very first thing you'll do, to test if the power transistor (igniter) is working or not, is to make sure the distributor is getting power (12 Volts).

If you haven't read the section: How Does The Power Transistor Work?, do so now. This section will give you an overview of the basic working theory of the power transistor and will help you see the 'why' of the tests in this article.

Alright, this is what you'll do:

  1. 1

    Disconnect the distributor from its electrical connector.

  2. 2

    Place your multimeter in Volts DC mode.

  3. 3

    With the red multimeter test lead, probe the wire labeled with the number 5, in the photo above.

  4. 4

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

  5. 5

    Now, turn the key on (you don't have to crank the engine).

  6. 6

    Your multimeter should display 10 to 12 Volts DC.

Let's interpret your voltage test result:

CASE 1: Your multimeter registered 10 to 12 Volts. This is the normal and expected result and confirms that the distributor is getting power.

The next step is check that the power transistor is getting its Triggering signal from the fuel injection computer. For this test go to: TEST 2: Testing The Power Transistor's Triggering Signal.

CASE 2: Your multimeter DID NOT register 10 to 12 Volts. This test result eliminates the power transistor as bad since without power (12 Volts) to the distributor, it won't work.

Although it's beyond the scope of this tutorial to troubleshoot this missing voltage, finding the cause of these missing 12 Volts will solve your 'no-spark no-start' condition on your 2.4L Nissan Altima.

Nissan Vehicles:

  • Altima 2.4L
    • 1997, 1998, 1999, 2000, 2001