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PAC OS-1 Wiring Interface

Connect a new car stereo and retain OnStar® in select GM vehicles

Item #: 127OS1

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PAC's OS-1 interface lets you replace any General Motors radio (without RDS) while maintaining operation of the OnStar® system. The OS-1 has on-board switching and built-in amplification that allows audio from the OnStar® system to play through the two front factory speakers when OnStar® is active, while muting the replacement radio.

The OS-1 can also send OnStar® audio to an external set of speakers if desired. There are separate right and left gain controls for OnStar® audio, and an LED indicator that turns on when the OS-1 receives an "On" command from the OnStar® system. Dimensions: 4-13/16"W x 1-1/16"H x 2"D. 1-year warranty.

Note: The OS-1 will interface with all GM radios that do NOT have the "RDS" option — it works with Bose and standard GM radios. If there is an "RDS" logo on the radio face, the OS-1 will not work.

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.

PAC OS-1 Wiring Interface Reviews

Average Customer Review:

5 Reviews

simple but not that simple

Written by: Anonymous from memphis, tn on October 20, 2010

Crutchfield Customer Review (What's this?)

I like that idea of the device bet, the harnesses are not mark. Makes is hard to
figure out.



Works as advertised

Written by: CodyT from Tucson, AZ on October 9, 2009

Crutchfield Customer Review (What's this?)

Works as advertised - all the wire colors match and it's an easy connection to the head unit.
Fit easily behind the vent controls in my 2002 Yukon (Tahoe)

Note that you don't need the other harness adapter if you use the PAC



PAC OS-1 Wiring Interface

Written by: Dondi from Waldorf, MD on March 16, 2008

Crutchfield Customer Review (What's this?)

Awesome. Works perfectly.



Onstar Retained!

Written by: Mark from Rhinebeck, NY on August 31, 2006

Crutchfield Customer Review (What's this?)

I needed to maintain the ONSTAR service in my 2001 S10 Blazer after installing a new KENWOOD KDC-MP2032. This device enabled me to do that. Installation was a breeze and everything worked as described.

My only complaint is that you need to set the volume at a consistent level before you button up the installation. With the OEM radio, the volume can be controlled while engaged with the ONSTAR service rep. It's not that big a deal, but worth mentioning .



PAC OS-1 Wiring Interface

Written by: Michael from Bend, OR on October 14, 2005

Crutchfield Customer Review (What's this?)

Installed this in conjunction with an Alpine deck for my 2002 Tahoe. The harness that came with unit made it possible for me to connect the deck harness to this OnStar interface harness on the bench instead of in the car, which was great. Connecting up the new deck became a simple connection of a few connectors and the antenna as opposed to acrobatic wire crimping. Only complaints I have are: 1) a smaller unit would be nicer, 2) there is a "tick" over the speakers when you engage and disengage an OnStar call, 3) wish it were less $. Otherwise, this unit works great, installed easily, and otherwise simplified my installation greatly.



Hands-on research

What's in the box?

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  • 1 GM OnStar Interface adapter with 7" OS-GM9 Molex plug and a 44" ground wire
  • One 12" OS-1618 harness
  • One 6.5" OS-RAD harness
  • One 6" OS-GM21 harness
  • Instructions

Product Research


Applications: The OS-1 is an interface that allows for the replacement of a GM factory radio that doesn't have RDS, while maintaining the operation of the OnStar navigational system. The OS-1 has onboard switching and amplification that allows the audio from the OnStar system to play through the front speakers when OnStar is active, and mutes the replacement radio. 

Left and Right Gain Controls: The OS-1 adapter has independent left and right controls that adjust the level of audio coming from the OnStar system.

LED Indicator: This is an indicator on the OS-1 that lights up when OnStar is active.

Harnesses: The harnesses allow the OS-1 to be installed in either a Bose or Non-Bose factory system. Refer to the instructions for specific information on wiring configuration for your particular application.

Inputs/Outputs: On the left side of the adapter, there is an 18-Pin Male Molex plug. On the right side of the adapter, there is a 16-Pin Male Molex plug, and there is a 7" harness with a 9-Pin OS-GM21 connector. Refer to the instructions for specific information on wiring configuration for your particular application.

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