For immediate integration, locate connector C1 on the rear of the head unit–it houses 18 pins split into two rows: upper (A1–A9) and lower (B1–B9). Pin A4 delivers switched +12V (orange/black stripe), critical for memory retention; verify continuity with a multimeter before bypassing factory security features. The metering wire sits at A7 (gray, 0.5mm²), carrying ambient noise cancellation signals–tap here only if retrofitting active noise reduction.
Speaker outputs follow balanced impedance pairing: front left (positive: A8, gray/yellow; negative: B8, gray) and rear right (positive: A9, violet; negative: B9, violet/yellow). Ground (B1) is bare copper, 14AWG–solder directly to chassis if replacing harness. For aftermarket amplification, splice into the B6 (green/blue) high-level input, ensuring ≤100mV idle noise to avoid signal degradation.
Illumination control (A2, light green) requires variable voltage (0–12V); connect via a 200Ω resistor if converting to static LED backlighting. Antenna trigger (A6, pink) activates with ignition–use a fused relay (7.5A) to prevent parasitic drain if retaining manual operation. For OEM Bluetooth adaptation, interface module T-Conn utilizes A1 (solid orange) and B2 (white/red) for data–protocol operates at 9600 baud.
Verify all connections with a signal generator before final assembly; diode drops on power lines (A4, B4) should not exceed 0.3V. If static persists, check B7 (shield ground) for continuity–clean chassis attachment points with 3M Scotch-Brite and apply dielectric grease. Document each modification against the repair manual’s schematic #EL01906 for future diagnostics.
Electrical Connections for the 1999 Sedan’s Premium Audio System
Begin by locating the harness behind the factory stereo–identify the 14-pin white connector as the primary interface. Pin 1 (red) carries constant 12V power from the fuse box (10A fuse, slot 18), while pin 2 (black) grounds to the chassis near the glove compartment hinge. Confirm continuity before proceeding to avoid short circuits.
For speaker outputs, match the following color codes to their respective door units:
- Front left (+): Gray/blue stripe → Pin 8
- Front left (-): Gray → Pin 9
- Front right (+): Light green/black stripe → Pin 10
- Front right (-): Light green → Pin 11
- Rear left (+): Dark blue/red stripe → Pin 12
- Rear left (-): Dark blue → Pin 13
- Rear right (+): Pink/blue stripe → Pin 6
- Rear right (-): Pink → Pin 7
Illumination control wires (orange/white stripe) connect to pin 5–this powers the display dimming in sync with dashboard lights. The antenna trigger (blue/white stripe, pin 4) activates the motorized unit when the stereo powers on. Test each wire with a multimeter set to 12V DC before finalizing connections.
Aftermarket installations require a bypass for the factory amplifier. Cut the pink wire (pin 3) and splice it to the head unit’s remote turn-on lead, ensuring the new system recognizes the ignition signal. Failure to bypass may cause low volume or distorted audio.
For steering wheel controls, procure an adapter harness retaining the resistive values of the original buttons. The resistance ladder spans 0–4.7kΩ across the yellow/red (pin 14) and violet wires. Verify compatibility with ASWC-1 or Metra ASWC interfaces.
Secure all splices with solder and heat-shrink tubing; electrical tape degrades over time. Route wires away from moving components (e.g., pedals, climate control cables) to prevent chafing. Label each connection with masking tape for future diagnostics.
Before reassembling the dash, power on the system and verify:
- All speakers produce clean audio without rattling.
- Display brightness adjusts with headlight activation.
- Preset stations or Bluetooth pairs within 5 seconds.
- No warning lights appear on the instrument cluster.
Troubleshooting Common Issues
Static from rear speakers? Check the pink and dark blue wires for poor grounding–re-solder if necessary. No sound output? Confirm the pink wire carries 12V during ignition; a faulty ignition switch may require replacement. Flickering display signals a weak ground–relocate to a bare metal chassis point near the driver’s kick panel.
Locating the Audio System Connector Pin Configuration for a Late-90s Luxury Sedan
Begin by disconnecting the negative terminal from the vehicle’s battery to prevent short circuits while working on the electrical connectors. The factory audio interface on this model uses a 20-pin white harness plug, typically found behind the center console near the climate controls. Verify the connector color before proceeding–aftermarket units often use different layouts.
Examine the harness carefully: the top row contains 10 pins, labeled 1 through 10 from left to right, while the bottom row mirrors this arrangement. Pin 1 delivers constant 12V power, essential for memory retention in the head unit. Pin 2 serves as the ground reference, and failure to properly connect it will cause intermittent functionality or complete system shutdown.
For audio signal transmission, pins 5 (left front speaker +), 6 (left front speaker -), 7 (right front speaker +), and 8 (right front speaker -) handle the primary stereo output. Rear channel signals occupy pins 9 (left rear speaker +) and 10 (left rear speaker -), along with pins 13 (right rear speaker +) and 14 (right rear speaker -). Ensure polarity matches the aftermarket stereo requirements–reversing these connections will invert audio phase, degrading sound quality.
| Pin Number | Function | Wire Color (Factory) | Notes |
|---|---|---|---|
| 1 | Constant 12V | Yellow | Fused at 10A |
| 2 | Ground | Black | Must connect to chassis |
| 3 | Switched 12V | Red | Activates with ignition |
| 4 | Illumination | Light green | Dims with headlights |
| 5 | LF Speaker + | Dark green | 4Ω impedance |
| 6 | LF Speaker – | Gray | |
| 7 | RF Speaker + | Dark blue | |
| 8 | RF Speaker – | Violet | |
| 9 | LR Speaker + | Brown | |
| 10 | LR Speaker – | Pink |
Pin 3 provides switched voltage, energizing only when the ignition is turned to the “ACC” or “ON” position–ideal for powering non-memory-critical functions. Pin 4 controls the backlighting of the head unit, adjusting brightness in sync with the dashboard illumination. Some aftermarket stereos require this signal to enable proper dimming.
Check for additional signals on less common pins: Pin 17 may carry the amplifier turn-on lead (small blue wire) in models equipped with premium sound systems, while Pin 18 could be reserved for speed-sensitive volume adjustment (if present). These are not universal–test with a multimeter before connecting to prevent damage to sensitive electronics.
Problems with the connector often stem from corroded pins or broken locking tabs. Clean contacts with electrical contact cleaner, and if the plug is damaged, consider splicing new connectors rather than forcing a connection. Always secure the harness properly–vibration from the road can dislodge improperly seated plugs over time.
When testing, use a digital multimeter set to DC voltage: probe Pin 1 for 12V regardless of ignition state, and Pin 3 for voltage only when the key is in the “ON” position. Speaker wires can be verified by connecting a 1.5V AA battery briefly–correct polarity will emit a click from the corresponding speaker. Avoid applying power for more than a second to prevent damage to the audio system.
Step-by-Step Guide to Connecting an Aftermarket Audio System
Disconnect the vehicle’s negative battery terminal first to prevent short circuits. Locate the factory harness behind the original unit–it typically includes 12 wires: solid yellow (constant 12V), solid red (switched 12V), black (ground), blue/white (amplifier remote), and eight speaker wires (often color-coded with a stripe for polarity). Strip ¼ inch of insulation from each wire using wire strippers, then twist exposed strands tightly to avoid fraying.
Matching Factory and Aftermarket Connectors
Identify the aftermarket harness’s corresponding wires using the provided color chart. The constant power (yellow) must pair with the vehicle’s permanent 12V lead, while the switched power (red) links to the ignition-controlled wire–swapping these will drain the battery. Secure ground (black) to a metal chassis point with a bolt or screw, ensuring no paint interferes. For speaker connections, match positive (solid or lighter stripe) and negative (darker stripe) wires precisely; incorrect polarity causes phase cancellation, muddying audio.
Use crimp connectors or solder for permanent joins, then insulate each connection with heat-shrink tubing or electrical tape. Avoid twist-and-tape alone–vibration loosens untaped joints over time. For vehicles with steering wheel controls, acquire an adapter module compatible with the OEM interface (e.g., Metra ASWC-1) and follow its pinout diagram, as retrofitting without one disables these functions.
Testing and Finalizing Setup
Reconnect the battery, then power on the new unit to verify all functions: tuner, media inputs, and volume controls. Play a test track with distinct left/right separation (e.g., stereo recordings) to confirm speaker wiring accuracy. If distortion or rattling occurs, recheck ground connections and speaker wires for shorts. Adjust fade/balance settings to center output; improper adjustments indicate a polarity error. Secure the new unit’s mounting kit with provided screws, ensuring no wires are pinched behind the dash.
For models with factory amplifiers (common in luxury sedans), bypassing without a line output converter introduces excessive voltage to the new system, risking damage. Install a converter if needed, connecting it to the correct speaker-level inputs on the aftermarket harness. Double-check all connections before reassembling trim panels–loose components cause buzzing or interference at higher volumes.