PAC OS-4 Wiring Interface

Connect a new car stereo and retain safety warning chimes, OnStar®, rear seat controls, the factory amp and XM tuner in select 2006-up GM vehicles

  • PAC OS-4 Wiring Interface


  • PAC OS-4 Wiring Interface

  • PAC OS-4 Wiring Interface

  • PAC OS-4 Wiring Interface

  • PAC OS-4 Wiring Interface

  • PAC OS-4 Wiring Interface

Item #: 127OS4

Review Summary

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Original price $149.99
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Our take on the PAC OS-4 Wiring Interface

by Zak Billmeier

PAC's OS-4 interface lets you replace the factory radio in select 2006-up GM vehicles with premium or Bose® audio systems, while retaining use of OnStar®, all factory warning chimes, and audible turn signal indicators. You'll also retain the use of your factory-installed XM satellite radio, as well as the 5.1 audio system in equipped Cadillac vehicles. Warranty: 1 year.

Please enter your vehicle information or call an Advisor at 1-888-955-6000 to find out if this interface will work with your vehicle.

See more info on this item

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

Hands-on research from the Crutchfield Labs (what are the Labs?)

Product Research
What's in the box?

Download owner's manual

  • OS-4 GM LAN OnStar Retention Radio Replacement interface
  • CM-X Chime module
  • B-BAA20 GM antenna adapter (9.5")
  • OS-NAV harness (8.5")
  • OS-GMLAN29 harness (9.5")
  • OS-RADPWRAUDIO harness
  • Harness with center/sub RCA plugs (31")
  • Installation instructions

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team — they open the box, verify contents, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.


Overview: The PAC OS-4 allows you to replace your vehicle's original factory radio with an upgraded aftermarket radio. It interfaces seamlessly with the vehicle's computer data bus system. The interface will maintain operation of the OnStar system in vehicles with Bose Audio Systems, amplified audio systems, and systems without amplifiers. The OS-4 has on-board switching that allows audio from the OnStar system to play through the two front factory speakers. All warning chimes, audible turn signals, Bluetooth, and the Vehicle Rear Parking Assist system (if equipped) will be retained.

Compatibility: The OS-4 is compatible with the following General Motors vehicles (as of 1/4/2012):

Model Make Year
Buick Enclave 2007-up
Lucerne 2006-up
Cadillac Escalade 2007-up
DTS 2006-2010
SRX 2007-2009
Chevrolet Avalanche 2007-up
Equinox 2007-2009
Express 2008-up
Impala 2006-up
Monte Carlo 2006-2007
Silverado 2007-up
Suburban 2007-up
Tahoe 2007-up
Traverse 2009-up
GMC Acadia 2007-up
Savana 2008-up
Sierra 2007-up
Yukon 2007-up
Pontiac Torrent 2007-2009
Vibe (for OnStar retention only) 2009
Saturn Outlook 2007-2009
Vue 2008-2009
Suzuki XL-7 2007-2008

Note: Please consult the Crutchfield Car Selector for your vehicle's compatibility.

Compatibility Notes: When the OS-4 is installed, the following conditions will be applied:

  • The OS-4 will retain the use of the factory-installed XM receiver. Factory RSE (rear-seat entertainment) controls must be present for this feature.
  • This interface can be used to interface with the Bose amplifier even if the vehicle does not have OnStar.
  • The interface will work in amplified or non-amplified audio systems.
  • This interface retains the 5.1 audio system in equipped Cadillac vehicles.
  • Built-in Smart Mute circuitry will play OnStar through the front speakers and allow the RSE audio jacks continue playing the audio source selected by the RSE controls.

Optional RSE Retention Harness: The GMRSAV RSE retention harness (120GMRSAV, sold separately) lets you retain the rear seat entertainment system in these select GM vehicles. The GMRSAV provides an audio/video input to the factory overhead video screen from your new aftermarket radio, and provides the audio/video output from the rear seat control panel to the aftermarket head unit.


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PAC OS-4 Wiring Interface Reviews

Average Customer Review:

11 people say:

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5 out of 5

can't imagine not having it.

Written By mark, MA on Wednesday, July 23, 2014
Crutchfield Customer Review (What's this?)
sure does make it a lot easier. everything plugs in as it should.
makes it EASY! pre-wire and install. very good unit.
wire schematic does not exactly match unit colors. Tech support very good in helping.
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1 out of 5


Written By Tom, Cocoa, fl on Thursday, March 20, 2014
Crutchfield Customer Review (What's this?)
Go to the PAC web site and check out the tech reviews
Does not work without steering wheel controls for volume, you lose On-Star function
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3 out of 5


Written By SteveM, Fort Wainwright, AK on Sunday, March 09, 2014
If you do not have steering wheel controls for onstar be advised that the volume to onstar will be blasted and not able to be adjusted without custom modifications.
Crutchfield response on Monday, March 17, 2014
There is a way to adjust the OnStar volume during the installation. Our tech support guys reached out to Steve with the solution.
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5 out of 5

PAC OS-4 Wiring Interface

Written By Anonymous, Pittsburgh, PA on Tuesday, October 01, 2013
Crutchfield Customer Review (What's this?)
Works great. I was able to connect my stock radio hardness to my new Pioneer unit without have to butcher the stock harness. I had to purchase the PAC SWI-RC to connect to the OS-4 to retain my steering wheel controls.
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4 out of 5

Works great so far!

Written By Compatible with a few issues, Allen, TX on Monday, May 06, 2013
Crutchfield Customer Review (What's this?)
This works great in my 2007 Chvey Impala. It retains the On star, chimes and signal indicator, Bose system with amplifier and the OEM sirusxm receiver. I used with the PAC SWI-RC to retain steeering wheel controls. The chime is a little annoying but it's nothing you won't get used to in a week or two.
Very compatible, easy to install.
Chime sound, SiriusXM converted to RCA outputs.
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5 out of 5

Typical install, works better than expected

Written By Frank, Novi, Mi on Friday, March 08, 2013
Installed into a 2012 GMC Acadia Denali w/ factory Nav head unit (lacking in features), rear seat entertainment, Bose DTS. I installed a Kenwood DNX 7190 HD. You have to do the typical wire-to-wire splicing which matches very well with Kenwood's coloring. Instructions are a bit lacking, but adequate enough to get the job done right the first time. This allows your factory rear camera to be fed into your new head unit with a very simple modification to the suppplied wire harness which is explained very well (if your camera screen is NOT in your rear view mirror). The unit itself is rather large and could be challenging to fit into smaller dashboards. You do lose your factory chimes and they are replaced by ones that are almost identical. The turn signal, as others have mentioned is a beep rather than the nice click, but this is only a small nuisance. Despite what it says on Crutchfield's and even PAC's site, it DOES allow you to fade the radio front-to-rear with Kenwood 7190HD radio. You need the PAC SWI-RC to retain steering wheel controls and is also easy to setup. You also need a the GMRVD which retains the rear seat entertainment system. Overall I'm very satisfied. It gets 4 stars for being very good, it would get 5 if it were a touch smaller and had a nicer turn signal tone, but because it actually fades, I'll give it 5 anyway. Let's hope it's durable...
Retains functions as described, even allows fading with my setup. Excellent audio quality.
Bulky, turn signal sound could be more pleasant
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3 out of 5

It Works

Written By gs, IL on Wednesday, July 18, 2012
Crutchfield Customer Review (What's this?)
Purchased this for a '07 Cadillac SRX in which the stock radio (Bose amplifier, but no navigation head unit) died. This units works, but the turn signal sound is a bit annoying. Turn signals use to make ticking sound, but with this module they make a beep-beep sound. Kind of like a video game. I guess I'll eventually get used to it. I haven't tried to integrate the steering wheel controls, yet.
Keeps everything in the car's CAN bus happy. Rear parking assist started working again.
Turn signal sound is a bit strange. The connectors and wiring feel a bit cheap compared the stock GM stuff.
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4 out of 5

PAC OS-4 Wiring Interface

Written By Anonymous, Marshall, MN on Thursday, April 28, 2011
Crutchfield Customer Review (What's this?)
I bought the PAC OS-4 in place of the GMOS-LAN-01 so I could install my
Alpine CDA-117 in my 2009 Chevrolet Silverado! Read many reviews and
discussion boards on this matter as Crutchfield did not offer the OS-4 as an
alternative for the GMAS-LAN in my vehicle. Glad I did my research!

Retains: Door chimes, blinkers and Onstar
Does Not Retain: XM Radio

Retains: Door chimes, blinkers, Onstar and XM (through the vehicles DIC)
Plug and Play for PAC SWI-JACK

The PAC OS-4 is very easy to install! There are a few Cons
- Size
- Wires in 4 directions
- CM-X Chime module is a little annoying with blinkers but you get used to it! If
not you are able to unplug the module without losing your Onstar!

All in all a 5 star, but had to give it a four because of these few little things!
Definitely would take the PAC version over GM's version in a heart beat if you
have a newer vehicle as mine and you want an easy install and/or want to retain
your XM Radio without having to buy the expensive box or headunit! If you want
to retain your XM. Keep in mind you will need an AUX input on your receiver for
the XM to work!
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3 out of 5


Written By chris9510, ST Lous on Tuesday, May 04, 2010
I have a 2007, GMC Yukon XL, no nav, bose, with dvd. This is not an option under outfit
my car. I was recommended the Axxess GMOS-LAN-02 interface. To retain my factory
LCD screen and IR emitter, needed the PAC version, OS-3 or better. Since the OS-3 is
no longer made, bought this instead.
Pluses--comes with it's own chime, do not need to do all the monkey business like you
need to with the Axxess with RCA cables, grounding one wire to set the volume, etc. Use
the DIC to control the volume.
Negatives--documentation is lacking. Easier to install than any other harness for GM
vehicles. Comes pre-wired for the SWI-PS, just plug and program! Smaller unit than the
Axxess. Outboard relay for remote on lead. There are 2 ports to plug the harness into,
with factory amp and without. Let me give you a hint, if you are going to USE the factory
amp choose the With factory amp location to plug the harness into. If you are not going to
use the factory amp use the without factory amp. This sounds logical when I say it, but
when you're looking at the kit and there is no mention of which one to use in the
instructions, you can take this either way. Plugging into the wrong one messed up my
SWI-PS steering wheel control interface. Called Crutchfield tech support and they said to
call PAC. Called PAC and they said I had my wiring wrong, fix it and call them back!!
Figured it out myself with trial and error. Works good otherwise
1 out of 1 people found this helpful
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5 out of 5

Overall nice product

Written By Jason, Modesto,CA on Tuesday, April 07, 2009
Crutchfield Customer Review (What's this?)
The OS4 integration unit is easy to install and works as advertised, at least for the non-Bose system I have in my 2008 Tahoe. My one complaint is the CMX chime module. The 'ding' in fine, but the blinker tone leaves a lot to be desired. It sounds a lot like an 80's video game. While we are getting slowly used to it, its funny sounding.

otherwise it was easy to install and has quality wiring harnesses. The instructions are a bit 'busy' and are all over the place. They could be better organized and more clear about at times, but if you follow the wire chart its a simple hookup.
1 out of 1 people found this helpful
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5 out of 5

Almost perfect

Written By Kerry, Ft Worth, TX on Monday, March 23, 2009
Crutchfield Customer Review (What's this?)
Used this unit to replace a GMOS-LAN-02 which had a fatal flaw.
See my review there for details.

My installation: 2008 Silverado, Kenwood DNX-5120, factory Bose amp. (Truck came with standard MP3 radio, no nav.)

Pluses for the OS-4:
1. Mute function works perfectly.
2. Includes tie-in harness for steering wheel controls. (No hunting wires.)
3. Steering wheel controls work for Onstar now.
4. Has leads for parking brake, reverse, and VSS. (Important for NAV units.)
5. Uses speaker level outputs instead of preamp outs. While THEORETICALLY not as good, this is not an issue for 3 reasons:
a. Speaker level outputs on more expensive radios are quite clean.
b. The audio must pass through the interface anyway, which can introduce noise. (The Metra was not bad per se, but to me the OS-4 IS cleaner.)
c. Using speaker outs frees up the preouts for easy future system expansion, like a subwoofer :)

Other notes:
1. Turn signals sound better.
2. The instructions state: "Note: The RPO code UQA (standard digital Bose® amplifier) will not fade as the rear outputs of aftermarket radio do not adjust the amplifier."
I do not understand this statement, as my truck HAS the UQA amp and the fader works perfectly.
3. Crutchfield's site says the OS-4 does NOT fit my truck, but I can confirm that it DOES, and the instruction sheet states that it DOES fit.

Why not perfect? I think PAC could use the VSS to raise the volume of the turn signals at road speed.
8 out of 8 people found this helpful
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1 question already asked

How do I raise the volume on this harness it's to low?? [ steven  May 31, 2014 ]
3 answers
  • There is no adjustment. I mounted the chime under the dash just enough so you can't see it. That worked for me, I can hear it fine now [ MARCUS R   Jun 02, 2014 ]
  • This harness was intended to be used with the factory amp remaining installed, if you removed the factory amp (not the radio head unit, or your vehicle didn't have one you will have to use the speaker output connections instead of the line level connections to feed the factory amp. In addition you may need to check with PAC directly since Crutchfield does not offer the entire PAC line, and I had to buy the kit I needed direct from PAC. Good Luck [ PAUL   Jun 02, 2014 ]
  • You've got the amplified v. non-amplified connection wrong on the main module. You likely need to move your plug. It's confusing, but you're getting pre amp out levels instead of the full amp section in your head unit. You could switch them, but read the instruction again first. [ WILLIAM   Jun 01, 2014 ]

For a more in-depth review and enhanced detailed information on the PAC OS-4 Wiring Interface, please visit the Crutchfield website product page (/ISEO-rccbcspd/p_127OS4/PAC-OS-4-Wiring-Interface.html ).