TEST 7: Testing The Triggering Signal From The PCM
For the power transistor to activate the ignition coil, it has to receive the instructions do so from the fuel injection computer.
These instructions come by the way of a signal called the Triggering Signal (although this is not Nissan's technical name for it).
In this test, you're gonna' check to see if the power transistor is being supplied with it when the engine is being cranked.
For this test you'll need to use a multimeter that can read Hertz frequency since an LED light will not work here since the signal's frequency is so fast that you can not see it with an LED light.
NOTE 1: It's important that the battery be in a fully charged condition for this test.
NOTE 2: The photo above is of the Nissan Pathfinder's 6-wire connector. If your vehicle is not a Pathfinder (or QX-4), the colors of the wires will be different. This is no cause for concern because the circuit descriptions are the same.
IMPORTANT: The distributor must remain connected to all of its connectors to be able to test the signal. You'll need to use a back probe on the connector or a wire piercing probe on the wire to access the signal.
OK, let's get started:
Select Hertz (Hz) frequency mode on your multimeter.
Don't have a digital multimeter that can read Hertz frequency? See my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing.
Connect the red multimeter test lead to the wire labeled with the number 1 of the distributor's 6 wire connector with an appropriate tool.
Connect the black multimeter test lead to the battery's negative (-) terminal.
Once everything is set up, have your helper crank the engine while you observe the multimeter.
Your multimeter will register around 6 to 8 Hertz (Hz) on its display screen if the Triggering signal is present.
Let's interpret your test result:
CASE 1: The multimeter registered 6 to 8 Hertz (Hz). This is the correct test result.
You can conclude that the power transistor is fried only if you have:
- Confirmed that there's no spark coming out of the ignition coil (TEST 3).
- Confirmed that the ignition coil is getting power (TEST 4).
- Confirmed that the ignition coil's activation signal is missing (TEST 5).
- Confirmed that the power transistor is getting its activation signal.
Replacing the power transistor will solve your 'no-spark no-start' problem. Now, at the time of this writing the only way to buy a power transistor is to buy the whole distributor.
CASE 2: The multimeter DID NOT register 6 to 8 Hertz (Hz). Without this activation signal the power transistor will not activate the ignition coil.
Recheck all of your connections. If still the multimeter does not register the indicated Hertz values, this indicates that the camshaft position sensor (located inside the distributor) is defective.
You can find the camshaft position sensor test here: How To Test The Camshaft Position Sensor (3.3L V6 Frontier, Pathfinder, Xterra).
TEST 8: Other Causes Of A Misfire
So you've done all of the spark tests, and still your Nissan pick up (or mini-van, or SUV) is still running rough (rough idle) and/or the misfiring. well, here are a couple of suggestions that might help:
- The valve cover gaskets are leaking oil onto the spark plug wells and soaking the spark plugs and spark plug wire boots in oil.
- Over time, this oil will cause a misfire as the oil cooks and turns into carbon tracks.
- The photo above shows you what a carbon track looks like on the inside of the spark plug wire boot and on the ceramic insulator of the spark plug.
- Engine compression test
- One of the most overlooked diagnostic tests to find the root cause of misfire is the compression test.
- You'll need an engine compression tester of course.
- The engine compression readings between cylinders should not vary more 15%.
- Carbon tracks on the spark plug(s) and in the inside of the spark plug wires.
- The orange arrows in the photo above to what carbon tracks look like.
- Replace the components as affected with carbon tracks.
- Broken spark plugs.
- This usually happens at tune-up time, if you have dropped one on the floor.
- You power washed the engine (this is something that should never be done on any Nissan vehicle).
More Nissan 3.3L V6 Tutorials
If this tutorial was helpful, check out the others I've written for the 3.3L V6 equipped Nissan vehicles. You can find a complete list of tutorials here: Nissan 3.3L Index Of Articles.
Here's a sample of the tutorials you'll find there:
- Mass Air Flow (MAF) Sensor Test 3.3L Frontier, Quest, Pathfinder, XTerra.
- How To Test The Camshaft Position Sensor (3.3L V6 Frontier, Quest, Pathfinder, Xterra).
- Ignition System Wiring Diagram (1999-2004 3.3L Frontier And Xterra).
- How To Test For A Blown Head Gasket (3.3L V6 Frontier, Pathfinder, Xterra).
If this info really saved the day, buy me a beer!