Installation Instructions
Combined "Forward" / Reverse Breakout Harness
Subaru & Nissan 20–pin and
Subaru & Toyota 10+6–pin


My combined "breakout" harness allows you to add an amp or subwoofer to your factory head unit, without having to cut or splice into your factory wiring harness.

This guide is broken into sections for three different types of installation:

  • Adding an aftermarket subwoofer
  • Adding an aftermarket amplifier to amp your main speakers
  • Adding an Alpine Power Pack amplifier (to amp your main speakers)

Before you skip ahead to those sections, be sure to rear the next sections about wire colors and pin-outs, T–branches, and factory head unit EQ.

Wire Colors and Pin-outs

The wires on my harness follow the aftermarket standard for car audio equipment.  See the "After-market" column in my pin-out tables to look up the function for each color.  Most of the wires also have printed text labels (e.g., "LEFT FRONT POSITIVE", etc.).

Pin-out tables:

Watch out for the wires with stripes — the stripes are narrow and easy to miss.  It helps to work in bright light.


On my combined harness, these signals have "T" branches:

  • Ground (BLACK)
  • +12V Accessory (RED) Key–Switched power
  • +12V Battery (YELLOW) Constant–On power
  • Amp Remote Turn–On (BLUE/WHITE) {only on 10+6–pin harness}

Most OEM HUs do not have the amp turn-on signal.  For those, you may want to use the RED branch for your amp's remote turn-on input.  The plain BLUE wire is for power antenna control (for the antenna booster amplifier in most recent models).  You can't use that for an amp (it would only work while you listen to AM/FM, not disc, aux, USB, etc.).

The YELLOW branch is available for relatively low-current devices.  Some powered LOCs (Line Output Converter) and audio processors want constant power instead of key-switched.  People have also gotten away with using this for the main power for not-too-large aftermarket underseat subwoofers.

You shouldn't need to use the ground wire for a plain LOC, but could need it for a LOC with amp trigger circuit, or audio processor.

Rather than cutting off the T–branches, I recommend keeping them so they're available for future additions.

Insulate (individually) the ends of any of the T–branches that you don't use.  Or in the case of the BLUE/WHITE, in cars whose HUs don't supply the amp turn-on signal you can extract the entire wire to reduce the clutter behind your HU.

Factory Head Unit EQ

Recent Subaru HUs have some undesirable EQ characteristics, including attenuating bass frequencies sent to the rear channels as you raise the volume (making the fronts a better choice for a subwoofer).  On some OEM Clarion models, you can use hidden menus to flatten the EQ, allowing use of the rear channels for a sub.  See these threads:

This feature is also available on the Legacy/Outback Clarion model CE617U1 (number printed on front).

Sorry, I'm not aware of any similar menu options for OEM navigation HUs or OEM models made by other manufacturers (Matsushita, Panasonic, Kenwood, etc.).

Adding Aftermarket Subwoofer

You'll want to effectively "tap" into one pair of speaker outputs (fronts or rears).  Two ways to do this:

  • Use some kind of "vampire" tap (insulation displacement connectors) to bite into the wires on my harness, such as Posi-Taps, 3M Scotchloks, or similar.
  • Cut my speaker wires, and solder or crimp the cut ends back together along with the new wire going to your LOC, amp, or powered sub.

Search for threads on the various forums for guides on connecting the main power and ground leads to your amp or powered sub.

Adding Aftermarket Main Speaker Amp

Cut the speaker wires on my harness somewhere in the middles (between the two connectors).  If you're installing a LOC or audio processor behind your HU, you might want to cut the wires on the HU side longer so they can reach the device.

Connect the speaker output wires (from the HU side) to your LOC or amp.  Connect the outputs of your speaker amp to the wires on the car side of my harness.

Search for threads on the various forums for guides on connecting the main power and ground leads to your amp.

Adding Alpine KTP-445U Main Speaker Amp

The Alpine KTP-445U "Universal Power Pack" has been very popular with other Subaru owners.  Here are customized instructions to install this amp:

Cut the speaker wires on my harness somewhere in the middles (between the two connectors).  If you're installing the Alpine amp behind your HU, check if you need to cut the wires longer towards either the HU or car side of my harness to help everything reach.  Depending on where you locate the Alpine amp, you may need to extend the wires.

Connect the speaker output wires (from the HU side of my harness) to the Alpine amp.  Rather than cutting off the Alpine's RCA jacks, you could add male RCA plugs to my wires.  That would make it much easier to reuse the amp with an aftermarket HU later.

Connect the outputs from the Alpine amp to the speaker wires on the car side of my harness.

Connect the BLACK and YELLOW T–branches to the amp's power and ground leads (same colors).

For most OEM HUs that do not have a pin for amp remote trigger, connect my RED T–branch to the Alpine's BLUE/WHITE remote turn-on INPUT lead (on the Alpine's input harness — the same one that has the RCA jacks).  On the few OEM HUs that do have the amp turn-on signal, connect my BLUE/WHITE to the Alpine's BLUE/WHITE INPUT lead.

Unless/until you add additional aftermarket amplifiers, insulate the end of the Alpine's BLUE/WHITE remote output lead (on the Alpine's output/power wire harness).

© Copyright 2014 by David Carter.  All rights reserved.