The power transistor in your 1998, 1999, 2000, 2001, 2002, 2003, 2004 2.4L Nissan Frontier or 2001-2004 2.4L XTerra is the ignition control module (ICM) of the ignition system.
The power transistor is the one that activates the ignition coil to spark and if this bad boy (the power transistor) goes bad, your Frontier or XTerra won't start.
In this article, I'll show you a very easy way to troubleshoot the power transistor to find out if it's bad or not. This is an on-car test which does not require expensive scan tools or other expensive/exotic diagnostic equipment.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar El Módulo De Encendido (1998-2004 2.4L Frontier, Xterra) (at: autotecnico-online.com).
Important Tips And Suggestions
TIP 1: TEST 1 and TEST 2 require that you do them while the engine is cranking, so you have to take all necessary safety precautions. Think safety all of the time.
TIP 2: The battery in your Nissan Frontier or XTerra must be fully charged so that the engine can reach its maximum cranking RPMs for these tests to be effective.
TIP 3: This power transistor test assumes that your Frontier or XTerra does not start due to a lack of spark. If your vehicle does not start but you do have spark, this article will not help you.
TIP 4: The igniter (power transistor) is part of the cam sensor and is 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 Work?
What's gonna' help you to see the 'why and how' of the testing in this article is to understand how the power transistor works. In a nutshell, this is what happens:
- The power transistor is located inside the distributor and is part of the camshaft position sensor assembly.
- The camshaft position sensor assembly is really a crank sensor, since the fuel injection computer uses this sensor to control the creation of spark (thru') the power transistor and ignition coil.
- Now, when you turn the key and crank the engine (to start it), the cam sensor/power transistor get power thru' the wire labeled with the number 5 (see photo above).
- As the engine turns, the cam 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).
- 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: Verifying The Power Transistor Is Getting Power
If you haven't tested the ignition coil first, please do so first (it's important that you test the ignition coil first and make it's not sparking!).
The test for the ignition coil can be found here: 2.4L Nissan Frontier, XTerra Ignition Coil Test (98-04) (if the ignition coil is sparking, then the power transistor is OK and not defective).
OK, to get this show on the road, the very first thing to do is to make sure that the distributor is getting power (12 Volts).
Without these 12 Volts, nothing's gonna work.
Alright, this is what you'll do:
- 1
Place your multimeter in Volts DC mode.
- 2
With the red multimeter test lead, probe the wire labeled with the number 2 (see photo above).
- 3
Next, Ground the black multimeter test lead directly on the battery negative (-) terminal.
- 4
Now, turn the key ON (you don't have to crank the engine) and notice the multimeter's voltage reading.
Your multimeter should display 12 Volts DC.
Let's take a look at what your test result means:
CASE 1: Your multimeter registered 12 Volts. This is good and confirms that the distributor (mainly the components inside) is getting power.
The next step is check that the power transistor is being fed a Triggering signal from the fuel injection computer. Go to: TEST 2: Verifying The Power Transistor's Triggering Signal.
CASE 2: Your multimeter DID NOT register 12 Volts. Recheck your multimeter connections and retest. If you still don't see 12 Volts, then this result eliminates the power transistor as bad since without power the components that work in conjunction with the power transistor will not work and indirectly affect the power transistor.
Although it's beyond the scope of this article 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 Frontier or Xterra.
