TEST 6: Testing The Ignition Coil's Activation Signal
As mentioned earlier, the ignition coil gets an activation signal from the power transistor (which is the ignition control module).
In this test section we're going to make sure that this activation signal is present in the green (GRN) wire the ignition coil's 2-wire connector (as we crank the engine).
If the activation signal is present then we can conclude that the reason why the ignition coil did not spark in TEST 4 is because it is defective.
To test for the ignition coil's activation signal we're going to use an LED light. If you don't have one and need to buy one, check out this link: The LED Light Test Tool And How To Make One (at: easyautodiagnostics.com).
Alright, let's get started:
Disconnect the ignition coil from its electrical connector.
Connect the black lead of the LED light to the female terminal that connects to the GRN wire labeled with the number 1 in the photo.
Connect the red lead of LED to the female terminal that connects to the BRN wire labeled with the number 2 in the photo.
Have an assistant crank the engine.
The LED light should blink on and off the whole time the engine is being cranked.
NOTE: Don't worry about what the LED light does before or after your helper starts cranking the engine. The only results you're interested in interpreting are the results obtained with the engine cranking.
Let's examine your test result:
CASE 1: The LED flashed ON and OFF. This is the correct test result.
With this test result you can conclude that the ignition coil, on your 3.0L Nissan Quest (Mercury Villager), is bad only if you have:
- Confirmed that all of the spark plug wires are not sparking (TEST 1).
- Confirmed that ignition coil's high tension wire does not spark (TEST 3).
- Confirmed that the ignition coil's tower does not spark (TEST 4).
- Confirmed that the ignition coil is getting 10 to 12 Volts (TEST 5).
- Confirmed that the ignition coil is getting an activation signal (TEST 6).
Here's why: If the ignition coil is getting 10 to 12 Volts (TEST 5) and it's getting an activation signal (TEST 6) then it has to spark. Since your test result confirms that it does not spark, you can conclude that the ignition coil is defective.
Replace the ignition coil to solve the no-start problem on your 3.0L Nissan Quest (Mercury Villager).
CASE 2: The LED DID NOT flash ON and OFF. Without the activation signal the ignition coil will not spark.
Re-check all of your connections and repeat the test. If the LED light does not flash on and off then the next step is to test the power transistor (ignition control module). For this test go to: TEST 7: Making Sure The Power Transistor Is Getting Ground.
TEST 7: Making Sure The Power Transistor Is Getting Ground
If in test 6 you found that the ignition coil's activation signal is not present then your next step is to make sure that the power transistor is getting Ground.
Depending on the year of your specific 3.0L Nissan Quest (Mercur Villager), the wire that supplies Ground to the power transistor will be a black (BLK) wire or a black with red stripe wire of the power transistor's 3-wire connector.
This wire is labeled with the number 2 in the photo above.
These are the test steps:
Select Volts DC mode on your multimeter.
Disconnect the power transistor from its electrical connector.
Probe the terminal that connects to the wire identified with the number 2 with the black multimeter test lead.
NOTE: Gently probe the female terminal of the connector. Do not force the multimeter's probe into the terminal or it will get damaged.
Connect the red lead of the multimeter to the battery (+) positive terminal.
You should see 10 to 12 Volts on the multimeter without having to turn the key to ON.
Let's analyze your test result:
CASE 1: The multimeter displayed 10 to 12 Volts. This is the correct test result and lets you know that the power transistor has a good path to Ground.
The next step is to check that the power transistor is receiving an activation signal from the fuel injection computer of your 3.0L Nissan Quest (Mercury Villager). For this test go to: TEST 8: Testing The Power Transistor's Activation Signal.
CASE 2: The multimeter DID NOT display 10 to 12 Volts. This test result tells you that Ground is not present. Without Ground the power transistor will not activate the ignition coil.
Your next step is to repair the Ground wire. Since this is a chassis Ground, you can repair this wire by simply connecting it to the battery negative (-) terminal. Once you've repaired this Ground wire, repeat the test.