Complete WRX 2017 Radio Wiring Color Code and Connection Guide
Locate the gray harness connector behind the factory head unit–pins 8 ( illumination), 10 (ground), 12 (constant 12V), 16 (switched 12V), and 18 (antenna trigger) are critical. Splice into these wires using T-taps or solder-and-heat-shrink joints; avoid crimp connectors to prevent signal drop. Verify wire colors against a verified pinout chart, as factory manuals may vary.
Use a DMM set to DC voltage to confirm power delivery before connecting aftermarket components. Pin 12 should read 12V+/-0.5V with the key off; Pin 16 must drop to near 0V when the ignition is turned off. If readings differ, inspect the fuse box (F12 for constant, F16 for switched) or the main harness at the firewall.
For Metra 70-1703 or PAC RP4-SB7 wiring adapters, match harness colors precisely–red (switched), yellow (constant), orange (illumination), and black (ground). Connect RCA outputs from amplifiers to the harness’s purple/white (front left), gray/white (front right), green/white (rear left), and violet/white (rear right) wires, ensuring impedance matches (4-8 ohms).
Test the dimming function separately; illumination wire (orange) should adjust with dash lights. If dimming fails, trace the wire to the combination meter or fuse box (F10). Replace faulty bulbs or resistors if voltage fluctuates outside 0-10V.
T-tune the antenna booster by tapping the blue/white wire (antenna trigger) to a switched 12V source–factory settings default to 900 mA draw. Overcurrent can fry the amplifier; use a 2A fuse in-line. For non-factory satellite receivers, splice the pink/violet wire (mute signal) to prevent audio conflicts.
Subaru Performance Audio Integration: Step-by-Step Connections
Locate the factory harness behind the dashboard on the driver’s side–pinouts match the OEM 16-pin connector labeled “A” (power/ground) and “B” (speaker outputs). Cut the stock harness only after verifying continuity with a multimeter: pins 1-2 (constant 12V), 3 (illumination), 4-5 (ground), 6 (antenna trigger), 7-8 (left front +/–), 9-10 (right front +/–), 11-12 (left rear +/–), 13-14 (right rear +/–), 15 (parking brake sensor), and 16 (speed signal). Crimp connections using 0.5mm² wire for power (red/yellow) and 1.0mm² for speaker leads (blue/white stripes for rear).
- Avoid tapping into the CAN bus (pins 15-16)–aftermarket units seldom support Subaru’s proprietary steering wheel controls without a PAC RP4-FD67 adapter (splices SWI into MOST network).
- For amplified systems, run a separate 4-gauge power cable from the battery, fused within 18 inches, to the amplifier’s +12V terminal; ground directly to chassis near the strut tower for minimal resistance.
- Test each circuit before buttoning up: set multimeter to DC 20V, probe ground (pin 4) against each power lead–expect 12.6V constant, 3.5V illumination (with headlights on), and dynamic speaker outputs (0.5-4V AC with audio).
Finding the OEM Audio System Plug on Your Sports Sedan
Begin by removing the lower dash panel beneath the climate controls–it snaps off with minimal force. The harness connector sits directly behind the dual-DIN stereo unit, secured to the rear of the mounting bracket by a single 10mm bolt. Disconnect the negative battery terminal before handling any electrical components to prevent shorts or airbag deployment.
Trace the bundled cables down to the white or gray 20-pin plug; its unique latch-release design prevents accidental disconnection. Pin assignments follow Subaru’s J-spec layout: constant 12V on pin 1, switched power on pin 3, ground at pin 4, and speaker outputs grouped from pins 5–20, color-coded for each channel (front left = gray/red, front right = gray/black, etc.). Match these to aftermarket adapters labeled for the VA chassis to confirm compatibility.
Decoding Wire Colors and Roles in the Subaru Performance Sedan Audio System
Locate the harness connector behind the infotainment unit–pinout labels are typically silkscreened or molded into the plastic. Match each terminal to this reference to avoid misconnections:
| Wire Color | Function | Connector Pin | Voltage (nominal) |
|---|---|---|---|
| Black / Yellow stripe | Battery constant | 18 | 12 VDC |
| Red / White stripe | Ignition switched | 12 | 12 VDC key-on |
| Purple | Illumination dimmer | 5 | 0-12 VDC PWM |
| Gray | Left front speaker positive | 21 | 2-4 VPP |
| Gray / Black stripe | Left front speaker negative | 22 | Ground reference |
| White | Right front speaker positive | 2 | 2-4 VPP |
| White / Black stripe | Right front speaker negative | 3 | Ground reference |
| Green | Left rear speaker positive | 20 | 2-4 VPP |
| Green / Black stripe | Left rear speaker negative | 1 | Ground reference |
| Blue / White stripe | Antenna motor drive | 6 | 12 VDC on-demand |
Use a digital multimeter set to DC volts; probe the black/yellow lead against chassis ground–reading should hold steady regardless of ignition state. If voltage drops below 11.5 V, inspect the fuse link (10 A, panel position #15) and battery terminal clamps for corrosion. Speaker leads require an oscilloscope or 1 kHz tone generator to verify polarity; reverse polarity risks damaging the amplifier’s bridge circuit. The purple dimmer wire carries a pulse-width signal controlled by the dash rheostat; substitute a 1 kΩ potentiometer during bench testing to simulate brightness levels.
How to Integrate a New Head Unit with Your Factory Subaru Impreza System
Begin by disconnecting the vehicle’s negative battery terminal to prevent short circuits. Locate the OEM harness behind the dash–it’s a 24-pin connector labeled METRA 70-1761 for compatibility. Strip the aftermarket harness’s wires to expose 1/4 inch of copper, then match each color to the factory plug using a multimeter for voltage verification. The yellow (constant 12V) and red (accessory 12V) wires must connect to their corresponding pins–swap these incorrectly, and the unit won’t power on. Ground the black wire directly to the chassis using a 10-gauge ring terminal, avoiding paint or corrosion at the connection point.
Critical safety step: Identify the vehicle’s parking brake wire (light green/black stripe) and speed signal wire (violet) in the harness. These require proper splicing for legal compliance–interrupting the parking brake circuit triggers a dashboard warning, while the speed signal ensures GPS tracks movement accurately. Use T-tap connectors for both wires, securing them with electrical tape and strain-relief loops to withstand vibration. For steering wheel controls, integrate a Pac-Audio SWI-X module between the new unit and the factory plug, programming button functions via the module’s included software.
Finalizing Connections Without Factory Harness Damage
Verify every connection with a test light before reconnecting the battery. Power on the head unit and confirm all features: AM/FM reception, USB charging (minimum 2.1A output), and Bluetooth pairing. If the display dims inconsistently, locate the orange (illumination) wire in the harness and connect it to the factory dimmer circuit–failing this, daytime visibility becomes hazardous. For amplified systems, retain the Subaru OEM amp by tapping into the rear RCA outputs (white/purple and grey/purple wires) at the 8-pin amp connector. Secure all splices with heat-shrink tubing to prevent moisture ingress, then tuck excess wiring behind the glovebox using zip ties to avoid rattling.
Typical Problems and Solutions After Upgrading the Factory Audio System
Start by verifying the accessory power circuit if the new unit fails to turn on entirely. The 12V switched lead (typically orange or yellow) must connect to a live wire that activates with the ignition–often pin 4 or 6 on the OEM harness. Multimeters detect voltage drops; if below 11.5V under load, trace back to the fuse box (locations vary by trim, but F-10 or F-17 commonly supply this circuit). Ground connections (black, pin 15) frequently cause intermittent operation–ensure they attach to bare metal with no paint or corrosion. Replace factory crimp connectors with soldered joints for durability.
Illuminated buttons that stay dark point to incorrect dimmer wire integration. The factory harness uses a variable-voltage dimmer input (gray, pin 7), which newer aftermarket units interpret as a simple on/off switch. Use a test light to confirm the wire pulses between 0-5V when adjusting dashboard lights; if absent, bridge to a fixed 12V source–but this disables dimming. For Steeda or Cobb-installed cars, check the CAN bus interface; early models (pre-2018 facelift) require a bypass module to retain steering wheel controls, available from Subaru dealership parts departments as PN 86301FG020.
Static during FM reception or Bluetooth dropout often stems from antenna adapter mismatch. The OEM roof-mounted diversity antenna (PN 86001FE040) uses an amplified signal splitter; generic adapters (MOLEX 150212-0001) lack the inline 5V booster, causing weak signal. Replace the entire cable run if fraying occurs at the firewall grommet. For parking sensor interference (audible beeps through speakers), relocate the module’s ground wire (light blue/black stripe) away from the head unit harness–wrap it in foil and ground separately to the chassis.