About the PAC OS-2C-CTSX Wiring Interface

PAC OS-2C-CTSX
PAC OS-2C-CTSX
PAC's OS-2C-CTSX interface lets you replace the radio in 2003-07 Cadillac CTS and SRX models while maintaining operation of the OnStar® system, warning chimes, and rear parking assist chimes. OS-2C-CTSX will work with standard GM or Bose amplified audio systems. This harness also plugs right into a PAC steering wheel control adapter (not included) so you can retain those convenient controls. Warranty: 1 year.
Note: You'll lose the factory XM receiver and the ability to fade from front to rear speakers when you install an aftermarket stereo. This interface will not work with 2004-06 SRX models with Cadillac navigation radios. 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.
What's in the box:
PAC OS-2C-CTSX Wiring Interface owner's manual
- Radio replacement interface module
- Wiring harness
- Installation Instructions
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More details on the PAC OS-2C-CTSX Wiring Interface

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Features
Radio Replacement Interface: The PAC OS-2C-CTSX Radio Replacement Interface Module allows the installation of an aftermarket radio into select Cadillac CTS and SRX vehicles equipped with OnStar and factory amplified audio system, while retaining select factory features. It also supports PAC steering wheel control adapters (sold separately).
Vehicle Compatibility: The PAC OS-2C-CTSX Radio Replacement Interface Module supports 2003-2007 Cadillac vehicles with OnStar, Bose factory amplified audio system, and 16-pin/20-pin connectors.
Make | Model | Year |
Cadillac | CTS | 2003-2007 |
SRX | 2004-2005 |
Note: You may use this interface even if the vehicle does not have OnStar, but does have the factory amplified audio system.
Retained Features: The PAC OS-2C-CTSX radio replacement interface retains the following factory features of your vehicle.
- OnStar Compatible: The interface retains your vehicle's factory OnStar system. It allows audio from the OnStar system to play through the vehicle's two front speakers when OnStar is active, and mutes the output of your new aftermarket radio.
- Factory Amplifier: The PAC radio replacement interface lets you retain your vehicle's Standard or Bose factory amplifier. 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.
- RAP: Your aftermarket head unit will continue to operate with the vehicle's RAP (Retained Accessory Power) system. The aftermarket radio will stay on after the vehicle's key is turned off and then stays on for approximately 10 minutes or until a door is opened.
- Safety & Warning Chimes: The vehicle's factory safety and warning chimes are also fully retained.
Note: The interface does not retain the factory XM receiver, you will lose this option when the factory radio is replaced with an aftermarket head unit.
+12V/10A Accessory Output: The OS-2C-CTSX provides a +12V/10A switched accessory output; no more searching for switched +12-volts in the fuse box or kick panel.
Navigation Outputs: The PAC OS-2C-CTSX provides navigation outputs (VSS, Parking Brake, and Reverse) to help ease the installation process of an aftermarket navigation radio.
Optional Steering Wheel Control Adapter: The OS-2C-CTSX radio replacement interface supports PAC's SWI-CP2 or SWI-RC steering wheel control adapter (both sold separately), allowing you to retain your vehicle's factory steering wheel controls. The included wiring harness plugs directly into the compatible SWC adapter. You will need to program the SWC adapter.
Wiring Connection Chart: The included harness features the following wires which will need to be hardwired (solder or crimped) to your aftermarket head unit's wiring harness.
Wire Color | Function |
Red | +12 Volt Accessory (10A) |
Yellow | +12 Volt Constant |
Black | Ground |
Orange/White | Illumination |
White | Left Front Speaker + |
White/Black | Left Front Speaker - |
Gray | Right Front Speaker + |
Gray/Black | Right Front Speaker - |
Pink (2) | VSS (Vehicle Speed Signal) |
Violet/White | Reverse Output (+) |
Light Green | Parking Brake (-) |
Brown | Mute (-) |
Note: Installation tools, hardware, & accessories are not included & sold separately.
The PAC OS-2C-CTSX Wiring Interface replaces these items

- lets you replace the radio in 2003-up Cadillac CTS and SRX while maintaining operation of the OnStar® system and retaining door chimes
- retains GM or Bose® audio system
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Customer Q&A
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The wiring interface was exactly what I needed to keep my steering wheel controls and chime. It's easy to set up but if you haven't wired a head unit before I suggest you let a professional do it.
Kenneth from Harper Woods, MI