gm stereo wires

A GM 21‑pin radio wiring harness plugs into the vehicle radio connector and provides terminals for 12‑volt power, four speaker outputs, power antenna control, dimmer, and chassis ground. It handles the basic power and audio wiring needed for most aftermarket receivers but typically does not support factory navigation, steering‑wheel controls, or video.

Antenna adapters let you connect the factory antenna cable to an aftermarket radio (or an FM modulator) without cutting or modifying the vehicle wiring. That preserves the factory cable and simplifies installation, avoiding splices or permanent changes to the factory harness.

The 21‑pin harness plugs into the vehicle radio connector and provides terminals for 12‑volt power, four speaker outputs, power antenna control, dimmer, and chassis ground so the aftermarket receiver integrates basic power and audio functions. It does not generally carry signals for factory navigation, steering‑wheel controls, or video.

The 21‑pin harness does not carry signals for special factory navigation systems, factory steering‑wheel control interfaces, or video. Those features are not supported by this harness as listed and may require additional adapters or a different harness.