Complete Subaru WRX 2015 Radio Wiring Diagram and Color Codes Guide

To bypass factory head unit integration issues, disconnect the negative terminal from the vehicle’s battery first–this prevents accidental shorts during modifications. The main harness connector at the rear of the stock audio unit uses 14-pin Molex plug (part #86327CA020), with pin assignments as follows:

Pin 1: Switched +12V (yellow, 2.0mm²) – fuse #15 (10A) in the under-dash panel

Pin 3: Ground (black, 3.0mm²) – chassis point behind glove box

Pin 5: Front left speaker (+) (gray, 1.5mm²)

Pin 7: Front right speaker (+) (purple, 1.5mm²)

Pin 9: Rear left speaker (+) (light green, 1.5mm²)

Pin 11: Rear right speaker (+) (white/black, 1.5mm²)

Pin 2/4/6/8/10/12/13/14: Unused or antenna motor control

For aftermarket amplifiers, splice constant +12V (red, fuse #30 15A) from the OBD-II port connector–this retains power for clock memory. Speaker wires use resistance-coded polyester film; mismatched gauge will distort output. Verify polarity with a multimeter–positive leads register ~4Ω to ground, negative ~∞.

Steering wheel controls interface via CAN bus (AVC-LAN, 500kbps). The data link connector (OBD-II pin 14) carries the signal; use a Metra ASWC-1 or PAC SWI-JACK to retain functionality. Avoid tapping into the airbag clock spring–damage risks fault codes B1829 or U1000.

Understanding Your Vehicle’s Audio System Connections

Locate the harness behind the factory head unit–it’s color-coded for clarity. The 16-pin connector splits into distinct groups: power, speakers, and antenna. Match the following wires precisely to avoid signal loss:

• Battery (constant): Yellow (12V, 20A fuse)
• Ignition-switched: Red (accessory power)
• Ground: Black (chassis connection, essential for noise reduction)
• Illumination: Orange (dims with headlights)
• Antenna: Blue (standard DIN signal, requires 12V trigger)

Verify each wire with a multimeter before connecting aftermarket components. A faulty ground or reversed polarity will trigger static or shutdowns.

Speaker outputs use twisted pairs to cancel interference. Each pair has a solid color (positive) and matching stripe (negative): white/white-black (front left), gray/gray-black (front right), green/green-black (rear left), purple/purple-black (rear right). Cross-check impedance between units–OEM setups typically handle 4Ω loads, while some aftermarket systems require 2Ω stability.

If integrating an amplifier, splice the blue/white remote turn-on wire into the harness. This ensures the amp powers only when the stereo does, preventing battery drain. For steering wheel controls, retain the beige 3.5mm connector–aftermarket adapters (Metra ASWC-1, iDatalink Maestro) map these signals to new head units without cutting original wires.

For vehicles with factory navigation or Harman Kardon premium audio, note these deviations from base models:

1. Aqua wire carries CAN bus data–splicing here voids connectivity with dashboard displays unless using a specialized integration module (e.g., Axxess ASWC).
2. Pink wire (microphone input) must be terminated or shielded to prevent feedback in hands-free setups.
3. Additional purple/green wires handle rear camera feed–connector pin 11 and 12 require re-termination if relocating the screen.

Ignore online guides suggesting “T-tap” splices–these degrade signal integrity. Use crimp connectors with heat shrink tubing, solder joints, or Scotchlocks rated for 18AWG.

Test all connections before reassembling the dash. Play pink noise through each channel at 60% volume to confirm clarity. Static suggests a loose connection; distortion means incorrect impedance matching. For troubleshooting, reference the pinout in service manual section 54-6 (electrical):

• Pin 1-4: Front speaker channels
• Pin 5: Battery (yellow)
• Pin 6: Ground
• Pin 7: Illumination
• Pin 8-11: Rear speaker channels
• Pin 12: Ignition
• Pin 13: Antenna
• Pin 14-16: CAN bus/data

Retain the original connectors for resale value–cutting them complicates future OEM upgrades.

Matching the Ideal Aftermarket Head Unit Connector for Your Sport Compact Sedan

Start by locating the OEM plug behind the factory-installed audio system–it’s a 14-pin Metra 70-8114 or Axxess ASWC-1 interface designed specifically for this performance model’s harness layout. Avoid splicing wires directly; adapters from Scosche or iDatalink Maestro preserve factory functions like steering wheel controls and security systems without cutting original circuits.

Verify the connector type before purchase. The most compatible options include:

• Metra 70-8114 (standard for base trims)
• Axxess AX-AdSW (supports steering wheel integration)
• iDatalink Maestro RR (retains vehicle settings and door chime audio)

Check the color-coding on your vehicle’s plug: yellow (constant power), red (switched power), black (ground), and orange (illumination). Mismatched adapters risk damaging the amplifier or triggering error codes in the ECU.

For premium sound systems, select an adapter with built-in amplifier bypass. The factory Harman Kardon setup requires a separate signal converter–Metra’s AX-TOY21 or PAC’s RP4-CH11 handles this without requiring additional resistors. If installing a double-DIN unit, ensure the dash kit (like Scosche SU22B or Metra 99-8212) includes climate control relocation brackets to avoid obstructing vents.

Before finalizing connections, test each wire with a multimeter. Switched power should read 12V only when the ignition is on, while constant power maintains voltage even when the vehicle is off. A weak ground causes background noise, so attach it to an existing chassis bolt near the original mount point. If the unit powers on but no sound plays, the error typically lies in the speaker wires–confirm polarity and impedance (4-8 ohms for most aftermarket decks).

Retain steering wheel controls by programming the adapter. The Axxess ASWC-1 requires holding buttons 1 and 5 simultaneously for three seconds to enter learning mode, then follow the vehicle-specific sequence from the manual. Failure to program correctly results in unresponsive buttons or erratic behavior. For vehicles with EyeSight, avoid tapping into the reverse camera circuit–install a separate aftermarket camera instead.

Document each connection with photographs or labels before disassembling the original system. If the new unit lacks a built-in EQ, add a line output converter (LOC) to prevent distortion in the amplified system. Common issues like flickering displays or intermittent power often trace back to loose harness connections–secure each plug with dielectric grease to prevent oxidation.

Final step: Confirm all doors remain locked after testing. Factory anti-theft features may engage if the battery disconnects during installation. Reprogram the ECU by turning the key to the “ON” position for 15 minutes if error messages appear. Keep the original plug intact in case of future dealer diagnostics.

Step-by-Step Guide to Locating Power and Ground Connections in the Vehicle’s Audio Unit

Begin by disconnecting the negative terminal of the battery to eliminate the risk of short circuits. Remove the dashboard trim panel surrounding the head unit–this typically requires a plastic prying tool to avoid damaging clips. For this model, the primary constant power lead (12V) is a yellow wire, often bundled with red (switched power) and black (ground) wires in the main harness behind the stereo. Use a multimeter to verify voltage: probe the yellow wire while the ignition is off–it should register 12V consistently.

Identifying Switched Power and Remote Turn-On

The red wire serves as the switched power source, energizing only when the ignition is in the ACC or ON position. Connect the multimeter’s positive lead to the red wire and the negative lead to a known ground; turn the key to confirm a voltage spike. The remote turn-on lead (usually blue) activates the amplifier–trace it back to the factory harness connector, labeled C-54 for this trim variant. Ensure all connections are insulated with heat-shrink tubing to prevent corrosion or accidental grounding.

For grounding, locate the chassis ground point near the fuse box or behind the glovebox. The black wire from the audio harness must terminate here, secured with a 10mm bolt; scrape away paint or rust at the contact point for optimal conductivity. Test continuity by setting the multimeter to ohms–probing between the black wire and chassis should read near zero resistance. If interference persists, reroute the ground to a thicker gauge wire directly to the battery’s negative terminal.

Integrating a New Audio System with Factory Speaker Harnesses

Locate the OEM harness behind the dash panel–typically a 16-pin connector with colorful leads. Pinouts follow ISO 10487 standards: brown and brown/black (front right +/–), gray and gray/black (front left +/–), purple and purple/black (rear right +/–), and green and green/black (rear left +/–). Solder each aftermarket harness wire directly to the corresponding factory lead, using shrink tubing for insulation. Avoid tap splices; they degrade signal integrity over time and introduce resistance that weakens bass response.

Verify speaker polarity before connection. Factory harnesses often invert polarity on one channel to compensate for cabin acoustics. Use a 9V battery to test each lead: a positive pop confirms correct polarity, a negative suck indicates reversed wires. Correct any mismatches at the harness junction to prevent phase cancellation, which manifests as muted midrange and weak stereo imaging.

Additional Amplification Considerations

Factory harnesses include a 12V switched lead (yellow) and ground (black) rated for 10A. If adding an external amplifier, tap these leads upstream of the fuse box–never splice into the factory radio’s power feed. Install a 20A inline fuse within 18 inches of the battery for the amplifier’s power cable to prevent wire melt in case of a short. Use 4 AWG oxygen-free copper wire for runs exceeding 12 feet to minimize voltage drop.

Signal interference commonly originates from unsuppressed alternators or poorly routed RCA cables. Route RCA cables on the opposite side of the vehicle from power cables, maintaining a 12-inch separation to avoid alternator whine–a high-pitched whine audible during engine revs. If whine persists, install a ground loop isolator (GLI) rated for 2-channel systems between the aftermarket unit’s preamp outputs and the amplifier. Avoid cheap GLIs; they introduce distortion and roll off high frequencies.

Final Configuration Steps

After physical installation, configure the aftermarket unit’s high-pass filters (HPF) for door speakers at 80Hz and low-pass filters (LPF) for subwoofers at 100Hz. Factory door speakers (6.5-inch woofers with 1-inch tweeters) handle frequencies above 3kHz poorly; enable a 3kHz HPF to protect tweeters from clipping. If the system lacks a dedicated subwoofer output, use a line output converter (LOC) connected to the rear speaker wires (± leads) to generate a low-level signal. Adjust gain settings by playing a 50Hz test tone at 75% volume; set amplifier gain until the tone distorts, then back off 3dB for headroom.