Start by locating the factory radio connector behind the infotainment unit–pins A8 (left front +), A7 (left front –), A4 (right front +), and A3 (right front –) handle the door drivers. Rear channels split into B6 (left rear +), B7 (left rear –), B8 (right rear +), and B5 (right rear –). Verify each terminal with a multimeter set to 12V DC before attaching new components.
Bypass the amplifier wiring harness if upgrading to aftermarket amplifiers. The under-seat amplifier uses C2 connector–cut orange/black (+12V ignition), gray/black (ground), and pink/black (remote turn-on) wires at the rear of the junction box. Splice these directly into the new amplifier’s power terminals to avoid factory signal attenuation.
For subwoofer integration, splice into C4 connector: purple (+) and purple/white (–) for the factory subwoofer output. If adding a dedicated low-frequency channel, run 12-gauge oxygen-free copper wire from the amplifier’s subwoofer output to the new enclosure, ensuring a 60-amp fuse within 18 inches of the battery.
Factory tweeters run on separate harnesses–A-pillar tweeters connect via A10 (left +), A9 (left –), A6 (right +), and A5 (right –). Reuse these circuits for component speaker upgrades by crimping butt connectors to maintain polarities. If replacing tweeters, remove the foam baffles inside the A-pillars to access the mounting screws.
When routing new cables, avoid the steering column harness and fuse box–use existing loom paths behind the kick panels instead. Secure wires with nylon zip ties every 12 inches to prevent vibration damage. For fiberglass-insulated models, strip ½ inch of shielding before soldering to prevent short circuits.
Test each channel individually with a 1kHz sine wave at 0dB before finalizing connections. Use an oscilloscope or audio analyzer to confirm phase alignment–miswired polarities will cancel low frequencies. If static persists, check for corroded terminals at the B-CAM module behind the glove box.
Audio System Connection Guide for the 2016 GMC Pickup
Install rear door units first by splicing the light green (positive) and dark green (negative) leads from the factory harness directly into the new component’s inputs–match polarity precisely to prevent phase cancellation. Front door setups follow a nearly identical pattern, but use gray (positive) and dark gray (negative) wires instead. Test each pair with a multimeter before securing connections: consistent readings between 3-4 ohms indicate proper bridging.
Subwoofer integration requires tapping into the purple (positive) and black/purple stripe (negative) wires located behind the amplifier, typically found under the passenger-side dash. Use 16-gauge oxygen-free copper cable for runs exceeding 12 feet to minimize resistance; solder joints must be heat-shrunk to prevent corrosion from road moisture. Verify factory settings in the infotainment menu–disable “Speed-Compensated Volume” before finalizing adjustments to avoid inconsistent bass response.
Amplifier Retrofit Tips
Locate the brown (remote turn-on) wire behind the radio unit; this signal activates aftermarket amps when the ignition engages. Connect it to a relay if adding multiple amplifiers to avoid overloading the factory circuit. For OEM head unit retention, splice RCA adapters into the green and purple speaker wires–these carry low-level signals suitable for amp inputs. Ensure ground wires terminate at bare metal chassis points, not painted surfaces, to prevent unwanted noise.
Tweeter installations in upper door panels need 20-gauge wiring; the factory uses tan (positive) and tan/black stripe (negative) wires. Route cables away from window regulators to avoid damage during operation. Capacitors aren’t necessary for standard upgrades, but adding a 1-farad unit can stabilize voltage fluctuations during bass peaks with aftermarket subs rated above 500W RMS.
Dashboard replacements often omit the orange/white (illumination) and pink (accessory) wires–include these when swapping head units to maintain dimmer function compatibility. For Steering Wheel Control retention, use an ASWC-1 adapter; program it via the “GM” preset before finalizing the radio installation. Double-check door lock actuator proximity to speaker wiring–secure all harnesses with nylon ties to prevent rattles.
Troubleshooting Common Issues
Static from improper ground connections mimics blown fuses–reterminate all chassis grounds with a wire brush to remove oxidation. Whining noises escalating with engine RPM indicate alternator whine; install a noise filter inline with the power cable near the battery. If rear deck speakers produce no sound, verify the gray/violet wires at the junction block behind the rear seat–corrosion here is common after 80K miles.
Balance issues between left and right channels often stem from mismatched wire gauges–never mix 18-gauge with 14-gauge in the same circuit. For odd-numbered speaker configurations, tap into the tan/dark blue wires for center-channel outputs, but expect reduced volume unless recalibrating the factory equalizer settings. Always use dielectric grease on all non-soldered connections to extend longevity in humid or salt-exposed environments.
Finding Hidden Audio Lines in a Double Cab Truck
Begin at the driver-side kick panel–removing the plastic cover reveals a cluster of six wires terminated in either crimp connectors or a small plug. Front door harnesses typically split into 1.5 mm² twisted pairs: solid gray and gray-striped for the tweeter’s positive/negative, solid violet and violet-striped for the mid-woofer. Trace each pair rearward; they run inside a corrugated loom beneath the sill plate before entering the A-pillar conduit.
Dash and Center Console Path
Lift the gear shifter trim to expose the factory amplifier–or its empty mounting bracket if the truck was ordered without the premium system. Behind the bracket, the main audio harness exits through a rectangular grommet into the floor tunnel; colors here repeat in a thicker gauge (2.5 mm²) with added orange and orange-striped circuits for the subwoofer channel. Disconnect the 8-pin Molex plug before pulling back carpet; the grommet itself is held by a single 6 mm screw on the tunnel frame.
Rear seating area lines converge under the rear seat riser. Flip the riser upward; you’ll see two oval cutouts in the floor pan. Punch out the foam plugs; inside each cutout lie two separate looms–left side carries rear door feeds, right side carries the fold-down entertainment harness if equipped. Locate the purple/violet pairs for the rear full-range drivers; these terminate in push-on spade connectors clipped to steel tabs welded to the frame.
Door panels require a T20 Torx to remove the inner handle bezel. Once freed, pry the panel with a nylon trim tool–avoid metal hooks near the latch mechanism. Door harnesses exit the jamb through rubber grommets; tugging gently reveals an extra 20 cm of slack. Solid and striped wires share the same color coding throughout the cab, but rear door harnesses add a brown and brown-striped pair for the rear tweeters in extended models.
Front and Rear Audio Connector Color Standards
Locate the door-mounted and cabin sound systems using these standard harness color codes. Verify each pair before making connections to prevent reversed polarity or phase issues.
- Front Left (+): Light green (LT GRN)
- Front Left (–): Dark green (DK GRN)
- Front Right (+): Gray (GRY)
- Front Right (–): Black/white stripe (BLK/WHT)
Rear outputs follow a similar pattern but use distinct colors for easy identification. Twist pairs gently to maintain signal integrity.
- Rear Left (+): Purple (PPL)
- Rear Left (–): Yellow/black stripe (YEL/BLK)
- Rear Right (+): Dark blue (DK BLU)
- Rear Right (–): Light blue (LT BLU)
Check factory harness plugs for faded or mislabeled wires–common in vehicles with aftermarket upgrades. Use a multimeter to confirm continuity if colors appear inconsistent.
Ground and Power Integration
Ensure amplifier turn-on leads connect to the violet/white (VIO/WHT) wire for proper system activation. Ground the black (BLK) wire directly to chassis metal for noise reduction.
For premium sound systems, the tan (TAN) wire delivers remote bass control–route it to subwoofer amplifiers only. Avoid splicing this wire into full-range outputs to prevent distortion.
Recheck all connections against manufacturer service manuals if audio cuts out intermittently. Loose or corroded terminals often cause sporadic failures.
How to Connect Upgraded Audio System Cables Properly
Trim the factory cable ends back 1.5 cm using wire strippers, exposing bare copper. Check insulation integrity–frayed strands should be clipped flush to prevent shorts. Twist strands clockwise into a tight bundle; loose threads cause intermittent dropout under vibration.
Match positive and negative leads by color code: aftermarket harnesses often use red (hot) and black (ground), but verify with a multimeter. Set to continuity mode; probe factory connectors to confirm polarity before joining. Incorrect pairing inverts phase, creating hollow, weak sound.
Soldering vs. Crimping
Solder joints require flux-core solder and a 60W iron. Heat the junction evenly; the solder should wick into the strands without cold globs. Insulate with adhesive-lined shrink tubing–apply heat evenly until it conforms tightly, sealing against moisture ingress.
For crimping, select the exact barrel size; 16-14 AWG connectors crush cleanly with ratcheting crimpers. Avoid generic pliers–they flatten wires, reducing current capacity. Slide tubing over the crimp before joining, then shrink for strain relief.
Route new leads away from sharp edges and moving parts. Secure with spiral wrap or silicone tape every 10 cm; sagging cables tap against dash mounts causing buzz. Test each channel at low volume–hissing or distortion means a missed connection.