PAC OS-311B Wiring Interface

Connect a new car stereo and retain OnStar®, RAP, and safety warning chimes in select 2004-up Chevrolet and Pontiac vehicles

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  • PAC OS-311B Wiring Interface



Our take on the PAC OS-311B Wiring Interface

by Ken Nail

PAC's OS-311B wiring interface lets you replace the factory radio in select 2004-up Chevrolet and Pontiac vehicles, without losing the audible warning tones, turn signal indicators, and OnStar® functions. Warranty: 1 year.

Please enter your vehicle information or call a Sales Advisor at 1-888-955-6000 to find out if this model is compatible 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.

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What's in the box?

Download owner's manual

  • OS-311b GM/OnStar interface
  • CM-X chime module
  • 6" GM-antenna adapter
  • OS-LAN24b OEM adapter harness
  • OS-3RAD radio interface harness with in-line relay
  • 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-311b Radio Replacement Interface allows easy connection of an aftermarket stereo in select General Motors vehicles equipped with OnStar; please see "Outfit My Car" to confirm compatibility. The interface will maintain operation of the vehicle's OnStar system and speakers. The OS-311b has on-board switching to allow audio from the OnStar system to play through the two front speakers when OnStar is active. This interface also retains all warning chimes and the audible turn signal indicators.

Note: The OS-311b interface does not retain the factory XM receiver. You will lose the XM option when the factory radio is replaced with an aftermarket head unit.

Smart Mute Circuitry: The unit's built-in Smart Mute Circuitry will mute the radio and play OnStar through your vehicle's front speakers.

Steering Wheel Controls: If your vehicle has steering wheel controls (and the aftermarket radio is compatible) they can be integrated, including the OnStar control, using the optional PAC SWI-RC steering wheel control interface.

RAP System Compatible: The interface supplies your new radio with a 12 volt switched power, and allows your aftermarket radio to operate with your vehicle's RAP (Retained Accessory Power) system. The radio will stay on after the key is turned off and stays on for approximately 10 minutes or until the drivers door is opened.


  • OS-311b Interface:
    • Width: 6.712" (with cables)
    • Height: 1.075"
    • Depth: 2.026"
  • CM-X Chime Module:
    • Width: 2.144" (with cables)
    • Height: 1.037"
    • Depth: 1.534"
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PAC OS-311B Wiring Interface Reviews

Average Customer Review:

7 people say:

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3 out of 5

I'm sure it's great if I needed it...

Written By Brian, Phoenix, AZ on Tuesday, September 02, 2014
Crutchfield Customer Review (What's this?)
I was told that in order to keep my door chimes turn signal etc I would need this item, that wasn't the case in my 2007 Pontiac G6. I also don't have on star so throwing that in there seems like a waste of money too. The only real benefit that I got from purchasing this item is I retained the RAP feature of my car (after turning off the car the radio still goes until I open the door.) All in all I'm sure this product is great, but I don't need it, even though I was told I did. I feel like I paid for a bunch of extra features I will never use.
Comes with everything you need to retain certain stock features of your car.
My car didn't need most of what this set gives me, even though it was advertised that I needed it.
Crutchfield response on Wednesday, September 03, 2014
After seeing Brian's review, our Tech Support team investigated and saw that not all of these Pontiacs need this adapter. So, for cars without OnStar (or for those people who don't care about retaining OnStar), we're now recommending a different (and less expensive!) adapter. Thanks for the feedback.
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5 out of 5

Connection speed

Written By Tone40, Chicago, Ill on Thursday, February 27, 2014
Crutchfield Customer Review (What's this?)
I thought that with having a 2004 Chevy MALIBU with OnStar and replacing my factory radio, that it was going to turn into a headache. This adapter made the installation so easy to install and still keeping the vehicles alert chimes in place and not compromising any sound quality to my radio, simply awesome!!!
Plug and play simplicity
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5 out of 5

Works Great

Written By Jere, Loganville, GA on Friday, January 31, 2014
Crutchfield Customer Review (What's this?)
Worked Great. Just as described. Easy to install. Good directions.
Worked just as described. Easy to install.
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3 out of 5

PAC OS-311B Wiring Interface

Written By Anonymous, Seattle, WA on Wednesday, January 29, 2014
Crutchfield Customer Review (What's this?)
Everything was great and worked just as described. The only reason I gave it 3 stars was because not every part worked right. Specifically the steering wheel controls.
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3 out of 5

Not Bad

Written By Logan H, Chesterton, IN on Sunday, July 21, 2013
Crutchfield Customer Review (What's this?)
i still have all my warning chimes you honestly do not need this unit what so ever but i mean its not a bad product it does exactly what it says it will do
does its job
i now have an echoing chime for everything because original warning chimes still work
1 out of 1 people found this helpful
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2 out of 5

Not worth it

Written By Anonymous, Mentor ohio on Monday, July 23, 2012
Crutchfield Customer Review (What's this?)
This interface is not worth the money ... It is supposed to keep ur audible warnings and onstar functions. Well with no module in my car now I can tell u I still have all my warning sounds and I don't pay for onstar so I don't care if that doesn't work I returned this item and used te money to get a nicer headunit
2 out of 2 people found this helpful
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3 out of 5

Product isn't bad

Written By Travis O, Eagan, MN on Tuesday, August 30, 2011
Crutchfield Customer Review (What's this?)
The product iitself is not bad or faulty. It works and I have the chimes, turn signal sounds, etc. but it losses stars because it is so expensive and as far as most car owners are aware, it's practically necessary. This much for "Open Door" chimes? Luckily Crutchfield will give you this half off if you need it. I still wish I didn't have to spend extra $ on my speaker system to buy a component that will not even help my speakers.
3 out of 3 people found this helpful
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1 question already asked

I have an 09 Pontiac g6 coupe. I was wondering if this harness can still send a low signal to the amp in the monsoon sound system, or if it can adapted to add pre amp rca connectors so I can use the switchable outputs on the head unit I have? [ Lucas  May 02, 2014 ]
1 answer
  • I had to remove all elements of the monsoon system for the stereo and speakers I purchased to work. [ WILLIAM P   May 02, 2014 ]

For a more in-depth review and enhanced detailed information on the PAC OS-311B Wiring Interface, please visit the Crutchfield website product page (/ISEO-rccbcspd/p_127OS311B/PAC-OS-311B-Wiring-Interface.html ).

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