PAC OS2C-CTS Wiring Interface

Connect a new car stereo and retain OnStar®, warning chimes, and the premium amplified audio system in 2003-07 Cadillac CTS or SRX models

Item #: 541OS2CCTS

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15 Reviews

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PAC's OS-2C-CTS interface lets you replace the radio in 2003-up Cadillac CTS and SRX models while maintaining operation of the OnStar® system, warning chimes, and rear parking assist chimes. The OS-2C-CTS will work with standard GM or Bose amplified audio systems. Warranty: 1 year.

Note: This interface will not work with 2004-06 SRX models with Cadillac navigation radios. You'll lose the factory XM receiver and the ability to fade from front to rear speakers when you install an aftermarket stereo. Please enter your vehicle information or call an Advisor at 1-888-955-6000 to find out if this model is compatible with your vehicle.

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.

PAC OS2C-CTS Wiring Interface Reviews

Average Customer Review:

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nice results

Written By Philly kinda guy, Florida on Wednesday, May 27, 2015

Crutchfield Customer Review (What's this?)

Came quick, well packaged, a little confusing installation but finally got it going well. There is a lot of stuff to cram uhder the dash, very tight fit

Pros: Works well, what more can you ask

Cons: Large and good eyesight is needed writing is tiny

Pac wiring interface

Written By Aaron, South Portland Maine on Tuesday, April 21, 2015

Crutchfield Customer Review (What's this?)

This keeps my onstar and door chimes working

Pros: Door chimes work. No leaving lights on or keys in car.

Cons: A little expensive but worth it.


Written By Texas notorious, Burleson, TX on Tuesday, March 17, 2015

Crutchfield Customer Review (What's this?)

First one I received did not work for some reason. Customer support was amazing though and had a new one shipped the day I called in and at my house with in 2 days. Put the new one with no flaw at all. Keeps everything running like stock system.

Pros: Farely easy to wire up. Just read labels.

Cons: Doesn't have full instructions on what should be done once installed.


Written By Matt Z, Michigan on Monday, February 16, 2015

Crutchfield Customer Review (What's this?)

easy connection

Pros: plug and pray!! real easy hookup

Cons: none

Easy as 123

Written By PAC OS2C-CTS, Eagle Michigan on Saturday, January 17, 2015

Crutchfield Customer Review (What's this?)

Made the installation extremely easy.

Pros: Easy to install with easy to read instructions


Written By Churchi, Bakersfield ca on Monday, January 05, 2015

Crutchfield Customer Review (What's this?)

Got it set up first try

Pros: Plugs fit my car

Cons: Could label all wires just for ease an so it's easy to learn

Perfect Fit!

Written By BobY, New Jersey on Thursday, December 04, 2014

Crutchfield Customer Review (What's this?)

This item was a perfect application for installation of my aftermarket radio!

Pros: Ordering the right item was a breeze. The customer service rep gave me exactly what I needed to install my aftermarket radio.

Cons: None

Works well

Written By Bill, Northern VA on Thursday, April 10, 2014

Crutchfield Customer Review (What's this?)

OK, here is the down and dirty on this adapter. It's a great product, works well with my car. However, the instruction manual has TINY writing where it comes to whichg wires go where on each car - just tiny! Good thing the give the online version. Anywho, the wires from your harness plug directly into this units secondary harness, after you look up your car's wiring in the manual. It's pretty simple but a novice (like me) has to take their time on this. That said I did it per the book (and also watched it online) and it was a 1st time go - no issues.

So yes I say get it!!

Pros: Easy to connect and assemble.

Cons: VERY BULKY UNIT, and much more so when you coulpe this with several other modules like the steering wheel control module, the dinger and so on.. Not to mentione all the cables like RCA, back up cable, speakers blah blah (it's a lot of junk back there). But I made it fit!! Also, the manual has tiny very print in the appendex area - which is the most important part of this operation

PAC OS2C-CTS Wiring Interface

Written By Anonymous, Long beach, CA on Wednesday, March 05, 2014

Crutchfield Customer Review (What's this?)

It made the install in my car very easy all I had to do was put some wires together. And it still let me keep my factory amp. For the pice you get it for. It is worth it. Great product.

PAC OS2C-CTS Wiring Interface

Written By Anonymous, detroit mi on Monday, May 27, 2013

Crutchfield Customer Review (What's this?)

Piece of cake to hook up, works as it should.

Pros: Easy install

Cons: None

PAC OS2C-CTS Wiring Interface

Written By hamilton, marietta on Friday, April 19, 2013

Crutchfield Customer Review (What's this?)

Really great radio would highly recommend. Easy to install and tech support very knowledgeable. Would purchase products in the future


Written By fatboy, Clewiston, FL on Sunday, July 29, 2012

Crutchfield Customer Review (What's this?)

At first thought it was gonna be a nightmare at first glance but just follow the instructions given and by the time u know it you will be enjoying your aftermarket radio!!!

Pros: Detailed Instructions!!!!!!!

Cons: None!

This is Great!

Written By Tim H., Wakeman Ohio on Tuesday, May 08, 2012

Crutchfield Customer Review (What's this?)

Without this interface I didn't have the knowledge to install the unit in my cts, it just works perfectly, even the speeker wires colors are the same as the replacement stereo unit

Pros: everything

Cons: none

PAC OS2C-CTS Wiring Interface

Written By C.R, Winder, GA on Thursday, February 09, 2012

Work perfect in a 2007 CTS

Pros: Everything

Cons: Not one

PAC OS2C-CTS Wiring Interface

Written By Anonymous, Ansonia, CT on Monday, March 28, 2011

Crutchfield Customer Review (What's this?)

First unit i ordered didnt work. Crutchfield promptly sent . New unit that worked fine. Makes it difficult to mount head . Unit because of the size but after alot of work got it to fit..

Hands-on research

What's in the box?

Download owner's manual

  • OS-2C-CTS Radio replacement interface module (for GM vehicles with OnStar)
  • CM1 Chime output module
  • 13" Vehicle harness (OS-CTS)
  • 8" Radio harness
  • Radio Replacement Installation Instructions
  • Chime Module Installation Instructions

Product Research



Overview: The PAC OS-2C-CTS Radio Replacement Interface Module allows the installation of an aftermarket radio into select Cadillac CTS and SRX vehicles equipped with OnStar and a factory amplified audio system.

Note: You may use this interface even if the vehicle does not have OnStar, but does have the factory amplified audio system.

Vehicle Compatibility: The PAC OS-2C-CTS Radio Replacement Interface Module supports the following vehicles.

Make Model Year Restrictions
Cadillac CTS 2003-2007 All models
SRX 2004-2006 Only vehicles without factory installed navigation radios

Note: The OS-2C-CTS does not retain the factory XM receiver, you will lose this option when the factory radio is replaced with an aftermarket headunit. Due to the design of the factory amplified system, there is currently no way of fading from the front to rear with an aftermarket radio.

OnStar Compatible: The PAC interface module will maintain operation of the OnStar and factory amplified audio system. OnStar audio will play through the front speakers when active. Your vehicle's OnStar volume will not be adjustable (preset at medium level).

Warning Chimes: The PAC OS-2C-CTS also retains all warning chimes and vehicle rear parking assist chimes.

Steering Wheel Control Compatible (optional): The PAC OS-2C-CTS is compatible with PAC's Steering Wheel Radio Control Interface (541SWIRC, sold separately) for aftermarket radios.


Radio Replacement Interface Module (OS-2C-CTS):

  • Width = 6.455"
  • Height = 1.055"
  • Depth = 2.475"

Chime Output Module (CM1):

  • Width = 2.325"
  • Height = 0.915"
  • Depth = 0.925"

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 verify what’s in the box, 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.

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