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Axxess GMOS-13 Wiring Interface

Connect a new car stereo and retain audible warning chimes, Bluetooth®, factory amp, and OnStar® in 2005-09 Cadillac STS models

Item #: 120GMOS13

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Your Cadillac is a comfortable, powerful vehicle, but the factory stereo leaves something to be desired. The Axxess GMOS-13 wiring interface allows you to integrate an aftermarket stereo with the amplified sound system in your 2005-2009 Cadillac STS.

With this interface, you'll be able to enjoy great sound from your new receiver without losing the car's OnStar and Bluetooth functionality. You'll also retain the factory warning chimes and turn signal indicators that are lost when the factory radio is removed. Even if you don't subscribe to OnStar, you'll still need this interface to connect an aftermarket stereo.

The GMOS-13 interface also provides a 12-volt switched accessory output, along with the Mute, Parking Brake, Speed Sense (VSS) and Reverse outputs you'll need if you're installing an in-dash navigation receiver. Warranty: 1 year.

Note: Most vehicles will require additional installation parts — please identify your vehicle if you haven’t done so. You can also call an Advisor for more information.

Axxess GMOS-13 Wiring Interface Reviews

Average Customer Review:

2 Reviews

Kenwood for My Cadillac

Written by: Anonymous from Waldorf Md on September 29, 2013

Crutchfield Customer Review (What's this?)

Works just fine. Met my expectations



Works well

Written by: Anonymous from Cypress, TX on June 24, 2013

Crutchfield Customer Review (What's this?)

Straight forward installation. No splicing wires in the car. Instructions could be clearer about the volume adjustment. This adjustment impacts the sound quality.

Pros: works well

Cons: instructions could use improving

Hands-on research

What's in the box?

Download owner's manual

  • GMOS-13 Cadillac STS amplified OnStar interface module
  • 11" Wiring harness (with a 16-pin connector on one end and bare wires on other end)
  • 18-pin to 16-pin GM harness
  • 16-Pin harness with one stripped lead
  • Installation Instructions

Product Research


Overview: The GMOS-13 interface is designed to let you replace the OEM radio in a 2006-2009 Cadillac STS with an aftermarket unit and still retain full functionality of the factory amplifier and OnStar system, as well as all safety and warning chimes. The GMOS-13 will also retain the retained accessory power convenience features. This interface has the capability of adjusting chime and OnStar volumes as well. In addition to these features, the GMOS-13 has the required outputs for the installation of a navigation radio (including VSS, parking brake, and reverse outputs).

GM Vehicle Compatibility: The GMOS-13 is compatible with the following GM Cadillac vehicles.

Make Model Year
STS 2006-2009

Note: Please consult Crutchfield's Outfit My Car to see if your vehicle is compatible and what additional accessories will be needed.

OEM Steering Wheel Control Compatible (optional): The GMOS-13 features a right-angle 3.5mm connector that lets you keep your GM vehicle's OEM steering wheel controls via the optional Axxess Steering Wheel Control Interface (120ASWC1, sold separately).

OnStar & Chime Volume Adjustment: The volume is adjustable for both the OnStar output & the warning chime.

Wire Code Chart:

Wire Color Function
Yellow +12 Volt Constant
Red +12 Volt Accessory
Orange/White Illumination/Dimmer
Black Ground
Blue Power Antenna
Blue/White Amp Turn-On
Green Left Rear Speaker +
Green/Black Left Rear Speaker -
Violet Right Rear Speaker +
Violet/Black Right Rear Speaker -
Gray Right Front Speaker +
Gray/Black Right Front Speaker -
White Left Front Speaker +
White/Black Left Front Speaker -
Light Green Parking Brake
Blue/Pink Vehicle Speed Sensor
Green/Purple Reverse Wire
Brown Mute Wire
Black/Yellow OnStar Level Adjustment

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