TEST 5: Verifying The Ignition Coil's Switching Signal

How To Test The Ignition Coil Packs (GM 3.1L, 3.4L)

This is the final test step and a continuation of TEST 4. Depending on the results you'll obtain, you'll be able to say that the ignition coil or the ignition control module (ICM) is bad.

For this test, you can not use a test light. You'll need an LED Light for this test. Take a look at this LED Light tool here: The LED Light Test Tool and How To Make One. Also, this test is performed with the engine cranking.

CAUTION: This test has to be done with the engine cranking. Be careful and take any necessary safety precautions.

OK, with the ignition coil that isn't sparking (from its two towers) still off from the previous step (TEST 4)

  1. Place the red lead of the LED on the male spade terminal labeled with the + symbol.
  2. Place the black lead of the LED on the male spade terminal labeled Signal. This is the terminal that provides the Switching Signal.
  3. Have your helper crank the engine while you observe the LED Light.

    NOTE: Whether the LED Light comes ON or is OFF before and after you crank the engine does not matter. The only flashing or lack of that you need to worry about, is during the cranking part.
  4. If the ignition coil is being activated, the LED light will flash on and off while the engine is being cranked.

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

CASE 1: The LED flashed ON and OFF. This result confirms that the ignition module is good and that it's providing an activation signal to the coil that is not firing off spark from its 2 towers.

This test result also tells you that the ignition coil is bad. Replace the ignition coil.

CASE 2: The LED DID NOT flash ON and OFF. Then the ignition control module is fried. Replace the ignition control module. Why?

Here's why: The ignition control module is NOT providing the switching signal to the ignition coil.

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Buick Vehicles:

  • Century 3.1L
    • 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Regal 3.1L
    • 1994, 1995, 1996
  • Rendezvous 3.4L
    • 2002, 2003, 2004, 2005
  • Skylark 3.1L
    • 1994, 1995, 1996, 1997, 1998

Chevrolet Vehicles:

  • Beretta 3.1L
    • 1994, 1995, 1996
  • Corsica 3.1L
    • 1994, 1995, 1996
  • Impala 3.4L
    • 2000, 2001, 2002, 2003, 2004, 2005
  • Lumina 3.1L
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001

Chevrolet Vehicles:

  • Malibu 3.1L
    • 1997, 1998, 1999, 2000, 2001, 2002, 2003
  • Monte Carlo 3.1L, 3.4L
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Venture 3.4L
    • 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005

Oldsmobile Vehicles:

  • Achieva 3.1L
    • 1994, 1995, 1996, 1997, 1998
  • Alero 3.4L
    • 1999, 2000, 2001, 2002, 2003, 2004
  • Cutlass (Ciera & Supreme) 3.1L, 3.4L
    • 1993, 1994, 1995, 1996, 1997

Oldsmobile Vehicles:

  • Silhouette 3.1L, 3.4L
    • 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004

Pontiac Vehicles:

  • Aztek 3.4L
    • 2001, 2002, 2003, 2004, 2005
  • Grand Am 3.1L, 3.4L
    • 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005

Pontiac Vehicles:

  • Grand Prix 3.1L
    • 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003
  • Montana 3.4L
    • 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Trans Sport 3.4L
    • 1996, 1997, 1998

Isuzu Vehicles:

  • Rodeo 3.2L
    • 1993, 1994, 1995
  • Trooper 3.2L
    • 1992, 1993, 1994, 1995