Power Transistor Test and Ignition Coil Test 3.0L Nissan (1990, 1991, 1992, 1993, 1994, 1995)

This comprehensive tutorial will help you test the following ignition system components: ignition coil, power transistor, spark plug wires, and distributor cap.

This tutorial applies to the following vehicles:

  1. 3.0L V6 Nissan D21: 1990, 1991, 1992, 1993.
  2. 3.0L V6 Nissan Pathfinder: 1990, 1991, 1992, 1993, 1994, 1995.
  3. 3.0L V6 Nissan Pickup: 1994, 1995.

You can find this tutorial in Spanish here: Cómo Probar La Bobina Y Módulo De Encendido (1990-1995 3.0L Pathfinder y Pick Up) (at: autotecnico-online.com).

NOTE: You can find the camshaft position sensor test here: How To Test The Camshaft Position Sensor (1990-1995 Nissan Pick Up And Pathfinder).

WIRING DIAGRAM: Ignition System Wiring Diagram (1990-1995 3.0L Nissan Pick Up And Pathfinder).

Symptoms Of A Bad Power Transistor Or Ignition Coil

In a nutshell, when either the power transistor or the ignition coil fails, the engine is not gonna' start.

To be a bit more specific: When either one of these components fail the engine is not gonna' start because none of the six cylinders will get spark.

Symptoms Of A Bad Distributor Cap And Spark Plug Wires

It's very common for one or several spark plug wires to go bad. When they do go bad, they don't transmit spark to the spark plug they're connected to.

It's also common for one or several of the distributor cap towers to go bad. When this happens those distributor cap towers will not transmit spark to the spark plug wires that are connected to them.

You'll also see one or more of the following symptoms:

  1. Engine misfires.
  2. No power when accelerating the vehicle down the road.
  3. Idles rough.
  4. Bad gas mileage.
  5. Black smoke coming out of the tail-pipe.
  6. Rotten egg smell coming out of the tail-pipe.
  7. Smell of unburned gasoline coming out of the tail-pipe.
  8. Won't pass the state emissions test.

Basic Nissan Ignition System Theory

In a nutshell this is how the ignition system works:

  1. The camshaft position sensor starts to generate and feed two position signals to your Nissan's PCM (Powertrain Control Module=Fuel Injection Computer).
  2. Once the fuel injection computer receives the camshaft position sensor signals, it sends the power transistor an activation signal.
  3. Once the power transistor receives its activation signal, it activates the ignition coil by interrupting the ignition coil's primary current circuit.
  4. Once the ignition coil is activated by the power transistor, it starts to spark.
  5. The ignition coil's spark is transmitted to the center of the distributor's cap by a high tension wire.
  6. The distributor rotor then distributes the spark to the distributor cap towers.
  7. From the distributor cap towers the spark is transmitted to the spark plugs via high tension wires.

With the help of this tutorial you'll be able to check the ignition coil's high tension wire, the spark plug wires, the distributor cap, the ignition coil, the power transistor.

What Tools Do I Need To Test The Ignition System?

Although the tests in this article are easy and simple, you do need some specific tools to perform them with. Here's the list:

  1. An HEI spark tester
    1. You can see an example of this tool here: OTC 6589 Electronic Ignition Spark Tester).
  2. An LED light.
    1. You can see an example of this LED light here: The LED light Test Tool And How To Make One.
  3. Battery jump start cables.
  4. A multimeter.
    1. If you don't have a multimeter or would like to upgrade yours, see my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing.
  5. A helper.

An ignition system wiring diagram always comes in handy and you can find one here: Ignition System Wiring Diagram (1990-1995 3.0L Nissan Pick Up And Pathfinder).

Camshaft Position Sensor Circuit Descriptions

There are 4 wires coming out of the distributor's connector. This connector connects to the camshaft position sensor assembly that's located within the distributor.

Below are the circuit descriptions of all four wires (circuits):

Camshaft Position Sensor Circuits
Pin Wire Color Description
1 Green With Yellow Stripe (GRN/YEL) 120° REF Signal
2 Black With White Stripe (BLK/WHT) 12 Volts
3 Black (BLK) Chassis Ground
4 Green With Black Stripe (GRN/BLK) 1° POS Signal

NOTE: The 4-wire distributor connector pin out only applies to the 1990, 1991, 1992, 1993, 1994, 1995 3.0L V6 Nissan D21, Pathfinder, and Pick Up.

Power Transistor Circuits

Power Transistor Connector Pin Out (1990, 1991, 1992, 1993, 1994, 1995 3.OL V6 Nissan Pick Up And Pathfinder).
Power Transistor Circuits
Pin Wire Color Description
1 Blue (BLU) Ignition Control Signal
2 Black (BLK) Chassis Ground
3 White With Black Stripe (WHT/BLK) Power Transistor Control Signal

Ignition Coil Circuits

Ignition Coil Electrical Connector Pin Out (1990, 1991, 1992, 1993, 1994, 1995 3.OL V6 Nissan Pick Up And Pathfinder).
Ignition Coil Circuits
Pin Wire Color Description
1 Blue (BLU) Ignition Control Signal
1 Black With White Stripe (BLK/WHT) 12 Volts