GM 3.8L Ignition Control Module And Crank (3X, 18X) Sensor Test

This exam volition aid yous to pinpoint the problem to the ignition control module (ICM) or the crankshaft position sensor every bit the source of your auto's no-start condition. Before starting the tests yous must first check and verify that there's NO SPARK present at any of the gyre towers.

Why? Because the clearest indication that the ignition control module and the crankshaft position sensor are good is if there's spark coming from all of the spark plug wires. So if you haven't checked, stop at present and practise a spark test on all of the spark plug wires.

If y'all do need to test but the ignition coil packs sitting on tiptop of the ignition control module (ICM), here's the article for you:

  • How To Test The GM 3.8L V6 Ignition Gyre Packs.

For a list of all of the 3.8L articles in this site, bank check out the index:

  • GM 3.8L Alphabetize Of Manufactures.

En Español You tin find this tutorial in Castilian hither: Cómo Probar El Módulo De Encendido Y Sensor Del Cigüeñal GM three.8L (at: autotecnico-online.com).

How The 3.8L Ignition Command Module (ICM) Works

Hither is a fiddling background information to help yous diagnose this no-spark status. In a nutshell, when the system is working properly, at crank-upward and beneath 400 RPMs the ignition control module controls spark (by activating the three ignition coils that sit on acme of it) without help from the fuel injection calculator.

More than specifically:

  1. When you plough the key to start the engine, the ignition control module gets power (12 Volts) and Basis.
  2. Once the ICM gets ability, it in plough supplies power to:
    • The crank sensor.
    • The cam sensor (if equipped).
    • The 3 ignition coil packs sitting on superlative of information technology.
  3. As the engine cranks, the ignition module receives the creepo sensor signal.
    • The crank sensor signal is an ON/OFF type of signal that can be measured with a multimeter or an LED low-cal.
    • The crank sensor signal is also called the 'triggering signal' in this article.
  4. As soon every bit the ICM gets the crank sensor signal, information technology starts activating the ignition coils sitting atop of it.
    • The ignition command module does this by switching the ignition coils' master electric current ON and OFF in a base timing mode so that they'll start sparking abroad.
    • This ON/OFF indicate is referred to as the switching indicate thru' out the article.
  5. The ICM also sends a Fuel Control signal to the PCM (Powertrain Control Module = Fuel Injection Computer).
    • The PCM uses this signal to start activating the fuel injectors.
  6. In one case the engine starts and/or higher up 400 RPMs (anything to a higher place this and the reckoner considers the engine as having started), the ECM takes over spark timing and the activation of the ignition coils (thru' the ignition command module of course).

When does the ignition command module (ICM) create this switching signal? After receiving 12 Volts, Basis, and the Triggering signals from the crankshaft position sensor assembly (which is located behind the crankshaft caster).

The GM three.8L 3X CKP And 18X CKP Sensors

Location Of The Crankshaft Position Sensor. GM 3.8L Ignition Control Module And Crank (3X, 18X) Sensor Test

The crankshaft position sensor is two hall event sensors in one. In other words, the assembly is two crank sensors in one and in this article I'll besides show you how to test it.

One CKP sensor is called the 3X CKP sensor and the betoken it creates is chosen the Sync 3X CKP Indicate and the other i is chosen the 18X CKP and its signal the Crank 18X CKP Signal. Equally stated earlier, both of these signals are critical for the ignition control module to beginning the car (to commencement sparking the ignition coils).

Although an oscilloscope is the best fashion to bank check for the pulses from the crankshaft position sensor (3X CKP and 18X CKP) to the ignition control module, there'due south another manner that I've used successfully for a number of years. This is using an LED light.

This LED light you can purchase from any electronics store ( I buy mine from my local Radio Shack store). If y'all're curious as to what this LED low-cal looks like and how to make information technology, click here: The LED Light Test Tool And How To Make I.

If you have access to an oscilloscope, I have included photos of what the wave-forms should look like. Whether you utilize the LED low-cal, or a multimeter, or an oscilloscope, you lot'll be able to successfully diagnose this no-start condition! So, read on my friend.

What Will I Exam?

The ignition module test is a very straightforward and unproblematic test. This is what it's composed of:

  1. The get-go club of business organisation is to make certain the ICM is getting power and Basis.
  2. And so, you'll make sure that the crank sensor is also getting juice.
  3. The next step is to test the crank sensor signals.
    • Retrieve, there are two signals involved (in starting the engine) and that are produced past the same crank sensor.
  4. From the results you get you'll be able to pinpoint the problem to
    • The ignition control module.
    • The crankshaft position sensor.

    Or completely eliminate these as the cause of the no-start status.

As y'all can see from the above test summary, it'southward that piece of cake to test the ignition control module!

IMPORTANT- To perform all of the tests the battery MUST exist in a fully charged condition.