TEST 3: Testing The Power Circuit (12 Volts)

Testing The Power Circuit (12 Volts). How To Test The COP Coils (GM 4.8L, 5.3L, 6.0L, 8.1L)

The ignition coil needs power, in the form of 10 to 12 Volts to function. In this test section, we'll check that they're available on the wire labeled with the number 1 in the photo above.

Testing for this voltage can easily be done with your multimeter in Volts DC.

Here's the test:

  1. 1

    Remove enough of this plastic tube, that sheaths the coils connector's 4 wires, to expose them for testing.

  2. 2

    Disconnect the ignition coil connected to its connector and place your multimeter in VOLTS DC mode.

  3. 3

    Probe the circuit labeled with the number 1 (in the photo above) with the red multimeter test lead (using an appropriate tool to pierce the wire).

    With the black multimeter test lead probe the battery negative (-) terminal.

  4. 4

    Have your helper turn the key to the ON position.

    You should see 10 to 12 Volts on your multimeter, or if you're using a test light, the test light should light up.

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

CASE 1: If the multimeter registered 10 to 12 Volts (or the test light lit up), then the power circuit is OK and is delivering voltage. The next step is to test the ground circuit, go to: TEST 4: Testing The Ground Circuit.

CASE 2: If the multimeter DID NOT register 10 to 12 Volts (or the test light DID NOT light up), then the power circuit has a problem. This result eliminates the COP ignition coil as the source of the misfire condition. The power circuit is shared by all of the COP ignition coils.

TEST 4: Testing The Ground Circuit

Testing The Ground Circuit. How To Test The COP Coils (GM 4.8L, 5.3L, 6.0L, 8.1L)

The ignition coil is fed 2 different grounds. One is a chassis ground (which will confirm in this test) and the other is a PCM ground (supplied internally by the PCM).

The fastest and easiest way to check the ignition coil's chassis ground is by doing a simple multimeter voltage test.

These are the test steps:

  1. 1

    Disconnect the ignition coil from its connector and place your multimeter in VOLTS DC mode.

  2. 2

    Probe the circuit labeled with the number 4 (see photo above) with the black multimeter test lead (using an appropriate tool to pierce the wire).

    With the red multimeter test lead probe the battery positive (+) terminal.

  3. 3

    Have your helper turn the key to the ON position but don't crank or start the engine.

    You should see 10 to 12 Volts on your multimeter, or if you're using a test light, the test light should light up.

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

CASE 1: If the multimeter registered 10 to 12 Volts (or the test light lit up), then the chassis ground circuit is OK. The next step is to test the ground circuit provided by the PCM, go to: TEST 5: Testing The Low Reference Circuit.

CASE 2: If the multimeter DID NOT register 10 to 12 Volts (or the test light DID NOT light up), then the chassis ground circuit has a problem. Recheck all of your multimeter connections and retest. If still the multimeter does NOT register the specified voltage, then this result eliminates the COP ignition coil as the source of the misfire condition. You must find out the cause of this ‘open’ in this circuit.