Z31 Nissan PRW-2 Ignition Upgrade

What is a PRW-2

This PRW-2 install guide pertains to the following item, which goes by several names:

• Power Transistor Unit
• Ignition Control Module
• Ignitor Chip
• Ignition Transistor

This is the transistor that charges and discharges the ignition coil. It can be found on a number of distributor-equipped Nissans.

Interchange

Where to Find a PRW-2 Unit

You can get a PRW-2 unit from any of the following models:

• INFINITI M30 (1990 – 1991)
• NISSAN ALTIMA (1993 – 1997) — Located under the airbox
• NISSAN AXXESS (1990 – 1992)
• NISSAN D21 PICKUP (1990 – 1994)
• NISSAN MAXIMA (1989 – 1994) — Located near the distributor on a bracket
• NISSAN NX (1991 – 1993)
• NISSAN PATHFINDER (1987 – 1995)
• NISSAN PICKUP (1995 – 1996)
• NISSAN PULSAR NX (1989 – 1990)
• NISSAN SENTRA (1989 – 1994)
• NISSAN STANZA (1990 – 1992)

The unit you’ll be sourcing looks like this (PRW-2, but there is also a similar-looking PRW-1A):

PRW-2 ignitor module (some units may be labeled PRW-1A but look nearly identical)

PRW-2 Install: Pin Swap & Mounting

On the Z31 harness, located on your driver-side strut tower behind the headlight (where the main ignition components are), you will find your current PTU.

It probably looks like this.

The PRW-2 is not exactly plug and play, but it’s close. The issue with the newer PRW-2 is that two wires have been flipped, or two contacts need to be swapped on the Z31 harness. The procedure is simple and is outlined below.

1. Remove the black housing clip on the back of the Z31 harness gray connector to expose the seals on the back of the wires.
   • You do not interact with or poke the seals.
   • This step just allows you to pull the wires out.
2. Swap the black wire with the green/white wire. This is the only change needed to the harness.
   
   Pinout:

   • Blue – Signal to Coil and Tach
   • Green – Signal from ECU and CAS
   • Black – Ground

Note for early '84 models: If you had the 2-pin Power Transistor, you’ll need to swap over the later style connector. The wires are the same, but you are missing the black ground in your harness—so you must add a chassis ground to the black lead after swapping the pins.

How to Remove Pins

Insert a safety pin into the small rectangular hole just above the head of each contact pin from the inside of the connector. Lay the pin flat on top of the connector contact and slide it in gently until it stops.
Do not force it—gently pry downwards to move the retainer inside the connector up and away from the pin, while gently tugging the back of the wire.
Do not use generic pin removal tools; they are usually too large, too thick, or not long enough.

Final Installation

Once you’ve swapped the wires, you can then plug and play. Just find a good mounting location in the same area, ensuring you have solid metal-to-metal contact for proper heat sinking.

Benefits

The benefits of this modification include a smoother idle and quicker throttle response, as the PRW-2 uses a newer and faster transistor. As our cars get older and parts become more scarce, this upgrade will likely become even more common. Even aftermarket companies are beginning to replace the old part with the PRW-2, often including a small sub-harness to handle the wire swap for you.

Image courtesy of RockAuto.com