Ford Focus ST 2016 Radio Wiring Color Code and Harness Guide
Begin by locating the main harness connector behind the factory head unit–typically a 12-pin block with color-coded leads. Pin assignments follow this sequence: yellow (constant 12V), red (switched 12V), black (ground), and blue/white (amplifier remote turn-on). Verify voltage with a multimeter before disconnecting; even slight deviations indicate potential fuse or relay issues in the auxiliary power circuit.
For speaker outputs, note the impedance-matched pairs: front doors use 4-ohm woofers paired with 2-ohm tweeters, while rear pillars employ a single 4-ohm coaxial. Cross-reference resistance with aftermarket amplifier specs–mismatches above 15% will distort midrange frequencies or trigger thermal shutdown. Use a patch harness adapter (Metra 70-1773) to bypass factory EQ settings, preserving signal integrity.
Steering wheel control integration requires a resistor-based interface module (ASWC-1 or equivalent). Map functions via the vehicle’s CAN bus: volume +/- correlates to 1.2kΩ and 2.4kΩ resistances, while track skip uses 4.7kΩ. Check for harness shorts–erratic behavior often stems from frayed wires near the pedal assembly, where vibration accelerates wear.
For navigation or satellite receiver retrofits, allocate fused 15A circuits from the under-hood relay box. Route power cables through existing grommets near the firewall; avoid the driver-side kick panel to prevent interference with brake circuitry. Ground connections should terminate at the chassis bracing behind the glovebox–sand paint to bare metal for optimal conductivity.
Test phase alignment with a 1kHz sine wave before finalizing installation. Front and rear speakers should form a coherent wavefront; delays exceeding 0.5ms (measured via oscilloscope) indicate reversed polarity or poor solder joints. Secure wiring with heat-shrink tubing and zip ties–exposed conductors near the shift linkage risk grounding faults during gear changes.
Wiring Guide for the 2016 ST Model Audio System
Begin by locating the harness connector behind the factory infotainment unit–it’s a 12-pin black plug labeled C1040. Pin assignments follow this layout for power, speakers, and antenna control:
| Pin Number | Function | Wire Color | Notes |
|---|---|---|---|
| 1 | Constant 12V | Yellow/Red stripe | Fused at 15A |
| 2 | Switched 12V | Red | Ignition-dependent |
| 3 | Ground | Black | Attach to chassis |
| 5 | Front Left (+) | White/Blue stripe | 2Ω impedance |
| 6 | Front Left (-) | Gray/Blue stripe | |
| 7 | Front Right (+) | White/Green stripe | 2Ω impedance |
Use a multimeter to verify continuity between the harness and the vehicle’s fuse box for pins 1 and 2. If voltage drops below 11.8V, inspect the fuse (F75 for constant power) and wiring for corrosion or loose connections.
Aftermarket Integration Tips
For amplifiers, splice the constant 12V (pin 1) and switched 12V (pin 2) into the amp’s remote turn-on wire. Avoid connecting the ground (pin 3) to the same point as the amplifier to prevent noise interference. Speaker wires (pins 5-12) carry a weak signal–ensure they are twisted pairs to reduce electromagnetic interference.
Antennas require a 12V trigger (pin 8, violet/white stripe) for powered units. If installing a non-OEM antenna, confirm compatibility with the vehicle’s CAN bus protocol–some aftermarket models lack data communication, causing warnings on the dash.
For steering wheel controls, retain the factory wiring adapter (Metra ASWC-1 or equivalent). The data wires (pins 9 and 10, blue and purple) must remain intact; splicing them directly disrupts functionality.
Test all connections with the ignition in the “ACC” position before finalizing the install. A common fault is reversed polarity on speaker wires–confirm with a 9V battery for correct cone movement (positive pushes out, negative pulls in).
Identifying the Factory Head Unit Connector Terminals
Locate pinout labels molded into the plastic housing of the OEM harness–typically etched near each terminal slot. Verify connections using a multimeter set to DC voltage: probe ground (bare metal chassis or black wire) and each pin while cycling power modes. Pins labeled A4 (constant 12V), A7 (switched power), and A8 (illumination) must read 11–14V; B1 (left front positive) and B2 (left front negative) should register 4–8V AC during audio playback. Color-coding varies by trim but follows this pattern: yellow (battery), red (ignition), orange (dimmer), brown (ground), white/black (speaker leads).
Cross-reference terminal positions with aftermarket adapter charts–some harnesses invert pin order between generations. If resistance checks show infinite ohms on B1/B2 or B3/B4 (right channel), inspect for frayed wires at the back of the unit’s connector block or corrosion in the door jamb splice. Use terminal release tools to avoid damaging the housing; never force probes into occupied slots. For CAN bus-equipped models, pin A10 carries speed-sensitive volume data–interference here triggers error codes P1602 (communication fault) or B103A (amplifier mismatch).
Standard Color Codes for ST Trim Audio System Connections
Identify front door tweeters by locating the gray and gray/black leads. These terminate in a two-pin connector behind the mid-range driver; splicing must preserve the polarity–gray stays positive, gray/black remains ground. Rear deck tweeters follow the same logic, yet swap gray for purple and purple/black wires.
Front door woofers utilize discrete pairs: solid light blue for the positive terminal, light blue/white for the negative. Rear door woofers mirror this scheme with solid green and green/white. Verify continuity at the amplifier harness before soldering; mismatched connections induce phase cancellation detectable during frequency sweeps.
Subwoofer and Amplifier Harness Specifics
Locate the dedicated RCA harness beneath the dash; orange RCA cables feed the external amplifier. Power connections require 4-gauge red wire directly from the battery–omit fuse holders near heat sources. Ground wires terminate with a 10-gauge crimp at chassis point G304, located behind the glovebox. Ignore factory labels on the harness; rely strictly on color verification: solid red (constant +12V), yellow/black (switched +12V), black/orange (ground).
- Center console tweeter: tan and tan/white
- Dash tweeters: brown and brown/white
- Amplifier trigger: violet/red (remote turn-on)
- Illumination wire: dark blue/yellow (dims with dash lights)
Factory harness connectors use staggered blades; retain original connectors for warranty diagnostics. If upgrading, utilize Metra 70-1771 harness adapters–they map all four door pairs and dash tweeters correctly without altering impedance. For aftermarket head units requiring parking brake signals, connect violet/green wire to the parking brake switch output; bypassing activates video functions but voids regional compliance.
Test every splice with a multimeter set to resistance mode. Probe both wire ends–expected values fall below 0.5 ohms. Confirm speaker function by sending a 1 kHz test tone; left and right channels must register identical SPL readings at seated ear level. Any deviation suggests reversed polarity at the driver or amplifier–retrace wiring with factory color charts before finalizing installation.
Step-by-Step Guide to Removing the Factory Head Unit
Unplug the negative terminal of the vehicle’s battery before starting to prevent electrical shorts. Locate the fuse box cover on the driver’s side dash panel–pry it off using a flathead tool to access the retaining screws. Two 7mm screws secure the trim panel; remove them and set aside. Gently pull the lower dash trim away from the steering column, releasing the plastic clips without forcing them.
Remove the climate control knobs by pulling them straight outward–no tools required. Unscrew the two 8mm bolts behind the knobs holding the center console in place. Disconnect the hazard light switch connector by pressing the release tab and pulling the wiring harness apart. Slide the entire console upward to disengage the top clips, then lift it clear of the mounting brackets.
- Insert a trim removal tool into the gap between the head unit’s faceplate and the dashboard.
- Work the tool around the edges to release the spring clips holding the front bezel.
- Pull the bezel straight out once all clips are free; set it aside.
Locate the four 10mm bolts behind the exposed head unit. Use a socket wrench to remove them–two on top, two on the bottom. Slide the unit forward just enough to access the rear wiring connectors. Press the release tabs on each plug (one for power, one for antenna, two for speaker wires) and disconnect them one at a time. Lift the unit out of the dash cavity.
Inspect the empty cavity for leftover foam or debris. If installing an aftermarket unit, secure the mounting sleeve included in the installation kit to the dash using the provided screws. Feed the new wiring harness through the sleeve, ensuring no wires are pinched. Reconnect the battery terminal last to test functionality before reassembling trim panels.
Reattach all components in reverse order. Snap the climate control knobs back into place, ensuring they click securely. Lower the center console into position, aligning the top clips before pressing down firmly. Reinstall the two 8mm bolts and reconnect the hazard switch. Fasten the dash trim with the 7mm screws, then replace the fuse box cover. Double-check all connections before finalizing the reassembly.