Begin by locating the main integration harness behind the dashboard fascia on the driver’s side. The factory connector typically splits into two primary sections: the upper 12-pin block (white or grey) and the lower 6-pin block (black). Pin assignments follow this structure without deviation across trim levels.
Power feeds require precise handling–constant 12V draws from pin 10 (upper block, yellow), while accessory-switched 12V routes through pin 12 (upper, red). Ground connects to pin 11 (upper, black)–verify continuity with chassis ground before proceeding. Ignoring this risks permanent damage to the aftermarket head-unit’s firmware.
Speaker leads occupy the lower connector exclusively. Front left (+/-) channels terminate at pins 1/2, front right (+/-) at pins 3/4. Rear channels follow the same logic: left (+/-) pins 5/6, right (+/-) pins 7/8. Impedance must match the amplifier’s specs–4 ohms nominal–or signal clarity degrades under 80 Hz.
Parking sensors (if equipped) interface via pin 9 (upper, grey/violet), but aftermarket harnesses often omit this line. Disabling sensor inputs may trigger false alarms; bypass by splicing a 1k-ohm resistor between the sensor wire and ground. Antenna amplification draws 5V regulated from pin 14 (upper, blue/white)–ensure the replacement receiver supports this voltage or install an inline booster.
For navigation retrofit, tapped GPS data streams from pin 15 (upper, brown). Factory harnesses lack this circuit on base trims; source an OEM extension (part #86207AC000) or manually route a shielded coax pair. Always solder and heat-shrink connections–barrel crimps introduce micro-resistance over 3-6 months.
Conflicting wire colors persist between MY variants. Cross-reference with service manual section 86-50 or use a multimeter on continuity mode to trace each circuit. Miswiring the illumination dimmer lead (pin 16, orange/green) results in non-functional dash backlighting–divert this to an adjustable 12V tap or accept static brightness.
Electrical Connections for the 2003–2005 SF Platform Audio System
Locate harness connector B137 behind the factory head unit–it contains 12 pins arranged in two parallel rows. Pin 1 (top-left, blue/white) carries switched 12 V; pin 4 (green/black) delivers constant battery voltage. Ground occupies pin 12 (black). Left-front speaker uses pins 2 (white) and 3 (white/black); right-front sits on pins 8 (gray) and 9 (gray/black). Rear outputs are mirrored: left-rear on pins 5 (green) and 6 (green/black), right-rear on pins 10 (violet) and 11 (violet/black). Measure with a multimeter before termination–any voltage below 11.8 V signals corroded fuse box connections, typically fuse #15 (10 A).
Aftermarket Adapter Pinout
Metra 70-8113 adapter harness maps as follows: yellow to pin 4, red to pin 1, black to pin 12. Purple wire (subwoofer trigger) absent–manufacturers often omit it, so cap pin 7 (blue/yellow) with heat-shrink tubing to prevent shorts. Speaker wires follow Metra’s universal color code–white to white, gray to gray–yet Subaru’s rear outputs require inversion of positive and negative leads for proper phase alignment. Verify with a tone generator set to 1 kHz at 0° phase before final crimp; reversed polarity manifests as weak bass and center-image cancellation.
Illumination control resides on a separate 6-pin mini connector (white, labeled i10) adjacent to B137. Pin 1 (red/black) supplies +12 V illumination, pin 2 (brown/yellow) grounds the dimmer circuit; pins 3–6 remain unused in base trim. Connect Metra’s orange/white wire directly to pin 1–failure to do so keeps the aftermarket unit permanently dark. Resistance across the dimmer circuit should read 50–200 Ω; readings outside this range indicate burnt dash-lamp filaments or a faulty headlight switch.
Anti-theft wiring terminates at a two-pin connector (black) below the climate control unit: pink wire carries data, black/green provides ground. Splice pink into Metra’s pink wire only if retaining OEM security–otherwise leave unterminated and wrap with electrical tape. Shorting pink to ground triggers immobilizer within 30 seconds, audible as a single chime from the instrument cluster. Always disconnect negative battery terminal before splicing; retained accessory power after shutdown can corrupt the ECU’s learned values, causing cold-start hesitation.
Finding the OEM Audio System Plug in Your Vehicle
Begin by removing the center dashboard trim panel directly above the climate controls. Use a plastic pry tool along the lower edge, working upward in short increments to release the clips without cracking the plastic. The panel will pivot outward from the top, revealing a rectangular cutout where the head unit sits.
The factory harness connector is nested behind the mounting brackets on the right side of the cavity. It’s a 24-pin white plug with a distinctive lock tab on the top; push the tab upward to release it before attempting to unplug. Avoid pulling on the wires–grasp the plug body firmly to prevent bending the pins.
- Meter from the top of the cavity to the plug: 3.5 inches
- Color codes for key wires: constant power (yellow), switched power (red), ground (black), front left speaker (gray/black stripe), front right speaker (gray), rear left (green/black), rear right (green)
- Two additional pins carry the illumination signal (orange) and antenna trigger (blue)
If the plug isn’t visible, check for a small foam block or zip-tie securing it to the bracket–remove these first. On some models, the factory amplifier wires (purple/brown and purple/white) are tucked behind the heater core firewall grommet; trace them upward if you need to bypass the amp.
Quick Release Tips
- Disconnect the negative battery terminal before handling any plug to prevent short circuits.
- Label each wire with masking tape before cutting or splicing; mismatch risks burning out the new receiver.
- Test continuity between the harness and door speakers–if silent, the OEM amp is likely integrated and must be bypassed.
Press the new harness’s locking tab back into place only after verifying all connections. Reinstall the trim panel by aligning the top edge first, then snapping the bottom clips into place. If the radio powers on but produces no sound, revisit the amplifier bypass wires–these are the most common point of failure.
OEM Audio System Harness Color Codes and Pin Functions
Identify the factory harness connector by matching these standardized color codes–critical for direct integration without signal degradation. Miswiring risks permanent damage to amplifier circuits and speaker outputs. Always disconnect the battery ground lead before probing or splicing.
| Wire Color | Function | Voltage Range | Connector Pin |
|---|---|---|---|
| Black (solid) | Ground | 0V | A-1 |
| Yellow (solid) | Battery constant | 12V DC | B-8 |
| Red (solid) | Ignition switched | 12V DC (key-on) | B-2 |
| Blue (white stripe) | Amplifier remote turn-on | 12V DC (key-on) | A-4 |
| Gray (black stripe) | Front left (+) | 2-4V RMS | A-8 |
| Gray (red stripe) | Front left (-) | 0V (signal return) | A-7 |
| White (black stripe) | Front right (+) | 2-4V RMS | A-5 |
| White (red stripe) | Front right (-) | 0V (signal return) | A-6 |
| Green (black stripe) | Rear left (+) | 2-4V RMS | B-4 |
| Green (red stripe) | Rear left (-) | 0V (signal return) | B-3 |
| Purple (black stripe) | Rear right (+) | 2-4V RMS | B-6 |
| Purple (red stripe) | Rear right (-) | 0V (signal return) | B-5 |
Use a multimeter set to DC volts for confirming power leads. Attach the black probe to chassis ground and test yellow for 12V constant; red should read 12V only when ignition is in RUN or ACC. Blue/white must pulse momentarily during startup–absence indicates blown fuse or relay failure upstream.
Avoid twisting signal and return pairs during installation–twisted pairs introduce impedance mismatches, causing frequency roll-off or distortion above 5 kHz. Speaker wires carry polarized signals; reversing leads flips acoustic phase, nullifying stereo separation and bass response.
Factory plug 12-pin connector (A) and 16-pin connector (B) use female spade terminals–crimp new terminations with gold-plated 0.110” quick disconnects to prevent oxidation. Verify terminal retention force exceeds 5N before plugging harnesses together to avoid intermittent connections.
Aftermarket Head Unit Power and Speaker Wire Connections Explained
Locate the constant 12V supply wire–typically yellow–before connecting any aftermarket receiver. This wire maintains memory for presets and settings, and splicing it directly to the vehicle’s fuse box ensures uninterrupted power. Use a multimeter to verify voltage stability before finalizing the connection; fluctuations risk resetting the unit.
Ground connection demands a bare metal surface, free of paint or corrosion. The factory ground point near the chassis rail is ideal, but if unavailable, drill a new hole and secure the black wire with a self-tapping screw and star washer. Loose grounds cause static, distortion, or intermittent shutdowns.
Speaker outputs require correct polarity to avoid phase cancellation. Factory color codes vary, but aftermarket harnesses often label front left positive as gray, front right as white, rear left as green, and rear right as purple. Cross-reference with the vehicle’s service manual to confirm before stripping wires.
Avoid tapping into factory amplifiers by using a line-output converter (LOC) for RCA signals. Connect the LOC’s inputs to the rear speaker wires (often thicker than front wires due to amplifier integration) and adjust the LOC’s gain to match the new unit’s preamp voltage–typically 2V to 4V.
Illumination wire–usually orange or orange/white–feeds dimmer settings to the head unit. Connect this to the vehicle’s lighting circuit to sync brightness with dashboard controls. Skipping this step leaves the display at full brightness, distracting at night.
For vehicles with steering-wheel controls, an adapter harness is mandatory. Brands like Metra or PAC offer kits with plug-and-play compatibility, but soldered connections endure vibrations better than crimp connectors. Test each button after installation to confirm mapping matches the new unit’s menu.
Fuse the power wire with an inline fuse holder rated at least 15A. Position it within 18 inches of the battery terminal to protect the entire circuit. Overlooking this step risks electrical fires if the wire shorts against the chassis.
Final testing begins with the engine off: verify all speakers produce sound without distortion, check illumination dimming, and confirm steering-wheel controls. Start the vehicle to test accessory power; turn signals or wipers should not affect audio. If static persists, recheck grounds and RCA shielding.
- Yellow: Constant 12V (memory)
- Red: Switched 12V (accessory)
- Black: Ground
- Orange: Illumination
- Gray/white: Front left speaker (+)
- Green/white: Rear left speaker (+)
- White/black: Front right speaker (-)
- Purple/black: Rear right speaker (-)