OS-2X - Car audio interface PAC - Free user manual and instructions

Product Type	Vehicle Radio Replacement Interface
Compatible Vehicles	Select General Motors vehicles with Class II Data-Bus
Key Functions	Retains warning chimes, Bose amplifier, Rear Seat Entertainment (RSE), OnStar; provides RAP, VSS, illumination, reverse trigger, parking brake outputs
Power Supply	12V DC vehicle electrical system
Max Accessory Output Current	10 A
Outputs	Accessory, illumination, reverse (+), parking brake (-), Vehicle Speed Signal (VSS)
Inputs	Remote on, SWC direct connect, speaker level inputs (front/rear)
Connectors	Interface connectors 1-4, vehicle connectors 1-2, 2-pin for chime module, RCA for RSE audio
Programming	Via programming button on side; includes master reset, SWC calibration, SWC mapping
LED Indicators	1 LED: red (power), amber (programming mode), flashing green (SWC activity)
Adjustment Dial	Controls OnStar volume and volume level for Bose systems
Firmware Update	Via RadioPRO PC app and USB connection to computer
Chime Module	Included CMX module with 4-position volume selector
Physical Dimensions (approx.)	4.5 x 3 x 1 inches
Weight (approx.)	0.2 lbs
Operating Temperature	Vehicle interior environment (typical -20°C to 60°C)
Accessories Included	OS-2X interface module, CMX chime module, wiring harnesses, connectors, 2-pin cable
Installation Requirements	Basic wiring tools; professional installation recommended
Maintenance	Keep connectors clean; ensure firmware up-to-date
Safety Precautions	Disconnect vehicle battery before installation; avoid short circuits; mount away from moisture

Frequently Asked Questions - OS-2X PAC

How do I retain factory chimes after installing an aftermarket radio?

Connect the included CMX chime module to the 2-pin connector on the OS-2X. Mount it unobstructed, preferably under the dash pointing down. Adjust the 4-position switch on the module to set chime volume (1 loudest, 4 softest).

How do I adjust OnStar volume if my vehicle has no steering wheel controls?

Use the adjustment dial on the side of the OS-2X interface. During an active OnStar call, turning the dial changes the OnStar audio level in 10 steps. Alternatively, if SWC are present, use the volume buttons.

How do I program steering wheel controls for my aftermarket radio?

First, set the DIP switches on the OS-2X according to your radio brand (see manual table). Then press and hold the programming button until LED 1 turns amber and you hear two chimes. Release, then press and hold each steering wheel button in order (Volume Up, Volume Down, Seek Up, Seek Down, Preset, Answer/Hang Up, etc.). The LED will blink when learned. Skip missing buttons by pressing the programming button. Test by pressing any SWC; LED 1 should blink green.

Why is there no sound from my speakers after installation?

Check that all connectors are firmly plugged in. Ensure the aftermarket radio is powered and the accessory output wire (red) is connected. For Bose systems, verify the fader is not biased completely to front or rear. If using the OS-2X amplified output, ensure the connection is correct. Also check the brown mute loop: if not cut, OnStar activity may mute the accessory output.

How do I update the firmware on my OS-2X?

Download the RadioPRO PC app from the PAC website. Connect the OS-2X to your computer via USB (cable not included, but standard micro USB). In the app, select Firmware > Update Firmware, then choose the downloaded file. After update, disconnect and test operation.

How do I retain factory Rear Seat Entertainment (RSE) audio?

Connect the RCA outputs from the 12-pin vehicle connector (Vehicle Connector 2) to the auxiliary input of your aftermarket radio. Select the auxiliary input on the radio to hear RSE audio. The RSE system will power on with the ignition.

What does the adjustment dial on the OS-2X do?

It adjusts the overall volume level for Premium Bose systems (Y91/UQA) and also controls OnStar audio volume. For Bose, turn the radio to 3/4 volume, then adjust the dial clockwise until distortion is heard, then counter-clockwise slightly.

How do I connect for a vehicle with a factory Bose amplified system?

Use Interface Connector 3 and plug it into the appropriate port on the OS-2X (refer to diagram). For real-time speaker fading, use the 'amplified output' connection. Note that aftermarket radio features like High Pass Filters will interfere with proper fader function.

What does the brown mute loop wire do?

The brown wire in Interface Connector 4 (pin 23) is a mute loop. If not cut, it turns off the OS-2X's accessory output when OnStar is active. If your aftermarket radio has a mute input, cut the loop and connect the brown wire to that input to mute the radio during OnStar calls.

How do I perform a master reset on the OS-2X?

With the interface installed and key in ignition, press and hold the programming button until LED 1 flashes red (mode A). Release immediately. This resets SWC mapping, calibration, and SWI-DIRECT output to factory defaults.

USER MANUAL OS-2X PAC

Introduction and Features

The OS-2X interface allows the replacement of a factory radio in select General Motors vehicles with the Class II Data-Bus. Using this interface will retain factory features such as Warning Chimes, Bose Amplifier, Rear Seat Entertainment (RSE), and OnStar when the original radio is removed. The OS-2X provides data bus driven outputs such as retained accessory power (RAP), vehicle speed signal (VSS), illumination, reverse trigger and parking brake.

Important Notes

1. Aftermarket radio must have an auxiliary input in order to retain RSE audio.
2. Real time speaker fading on Premium factory Bose systems (Y91 / UQA) is only supported with the “amplified output” connection of the OS-2X.
3. When using real time speaker fading (Premium Bose only), if the fader setting is biased more to the front or rear, as the radio turns on the sound may begin at the default setting and then quickly transition to your custom setting.
4. Aftermarket radio features such as High Pass Filters (crossovers), DSP or “Network Mode” will interfere with proper fader function (Premium Bose only). In order for the OS-2X’s fader function to work, the audio from the aftermarket radio’s output must match so it can compare the front and rear audio levels and determine the proper fader setting for the factory amplifier.

Module Layout

Installation Steps

1. Wire your aftermarket radio to the OS-2X's harness according to the wiring connections chart below.
2. The Brown mute loop in Interface Connector 4 (if not cut) will turn the OS-2X's accessory output off when any OnStar function is active. If the aftermarket radio has a mute input, cut this loop and connect the Brown wire in pin 23 to it. This pin is located in the top row next to the solid blue wire. (The top of the connector has the locking tab on it).
3. Plug Interface Connectors 1 and 2 into the appropriate ports on the OS-2X interface (using the diagram on Page 1 or the label on the bottom of the interface).
4. The Interface Connector 3 connection will be dependent upon whether or not the vehicle has a factory amplified system. Plug this connector into the appropriate port on the OS-2X (using the diagram on Page 1 or the label on the bottom of the interface).
5. If the aftermarket radio is equipped with an auxiliary input and you wish to retain the factory RSE audio, plug the RCA connectors from the Vehicle Connector 2 into the radios auxiliary input.
6. Remove the factory radio and plug in the OS-2X's Vehicle Connector 1 and Vehicle Connector 2 into the factory vehicle harness.
7. Plug the 2-Pin connector into the CMX Chime Module (If the vehicle chimes when the radio is removed, the CMX is not necessary). PLEASE NOTE: In order to get the best possible sound out of the CMX, please mount it in a place free and clear of any obstructions, preferably as close as possible to the bottom of the dash pointing down toward the floor of the vehicle.

Close-up of a black connector with yellow wires and white connector on a textured surface (no text or symbols visible)

Interface Connector 1 (3-pin)

Close-up of a white connector with multiple colored wires against a dark textured background (no text or symbols visible)

Interface Connector 2 (20-pin)

Close-up of a white connector with purple and green wires attached to a dark textured surface (no text or symbols visible)

Interface Connector 3 (12-pin)

Close-up of a white plastic electrical connector with multiple wires against a textured gray background (no text or symbols visible)

Interface Connector 4 (24-pin)

Close-up of a white electrical connector with multicolored wires attached, placed on a textured surface (no text or symbols visible)

Vehicle Connector 1 (24-pin)

Close-up of a white plastic electrical connector with wires, placed on a textured surface (no visible text or symbols)

Vehicle Connector 2 (12-pin)

Close-up of a black CMX compact electronic device with visible ports and wiring (no text or symbols on body)

CMX Chime Module

Wiring Connections

Yellow 12v+
Red	Accessory Output(10 amp)
Black Ground
Brown Loop Mute Output
Blue Not Used
Blue / White Remote On Input
Orange Not Used
Orange / White Illumination Output
Purple / White Reverse Output (+)
Light Green Parking Brake Output (-)
Pink Vehicle Speed Signal(VSS) Output
11Pin White Connector	SWC Direct Connect
Purple / Black Rear R - input
Green Rear L + input
Green / Black	Rear L - input
Gray	Front R + input
Gray / Black	Front R - input
White	Front L + input
White / Black	Front L - input

Programming Button and Adjustment Dial Functions

You can press and hold the programming button on the side of the interface to access different programming modes. Once the LED is lit to the mode you desire (see below for modes), immediately release the programming button to access that mode.

PLEASE NOTE:

- This process must be done with the interface in the vehicle and the key in the ignition position.

A. LED 1 flash red: Master reset. This does a master reset of the interface and restores the following settings to factory defaults:

• SWC Mapping
• SWC Calibration

SWI-DIRECT Steering Wheel Control Output Connector

If you are using the SWI-RC-1 or SWI-CP2 please follow the steps below.

Refer to the figure to the right to set the bank of eight Dip-Switches.

Refer to the guide below for setting the bank of four Dip-Switches based on your radios manufacturer.

Set DIP-Switches that correspond with your radio to the ON position. Set all other DIP-Switches to the OFF position.

Alpine JVC	Kenwood / Lightning Audio	Stinger	Clarion / Nakamichi	All Other Brands	Pioneer Sony Fusion
1 2 1 & 2 3 3 1, 2, & 3	1, 2, & 3 4 1 & 4

If your brand is not listed above, please use "ALL OTHER BRANDS."

SWC Re-calibration Procedure (Corvette Only)

Please Note: This is only necessary if after installation, the SWC are acting erratic or unresponsive in the Corvette.

1. Turn the key to the ignition position.
2. Press and hold the programming button until LED 1 turns amber and you hear two chimes. When this happens, release the programming button.

3. Within 7 seconds, press and hold the button that is to be learned on the steering wheel. The LED will turn off when the button is pressed and begin blinking when the value has been learned. Once the LED begins blinking, release the button.

4. Repeat step 3 for each additional function on the steering wheel.

5. If you come to a button in the list that your vehicle does not have, skip it by pressing the programming button on the interface. Any buttons not learned during this process will not function.

6. Once programming is completed, the LED will flash indicating end of programming.

7. Test the interface for proper functionality. Whenever a SWC is pressed LED 1 on the interface should blink green. If any function does not work, repeat the programming steps.

Button Programming Order

Volume Up

Volume Down

Seek Up

Seek Down

Preset

Answer / Voice

Hang Up

Preset Up

Testing and Verification

1. Turn the ignition on. LED 1 will illuminate red and the +12v accessory wire will turn on.
2. Turn on the radio and check chimes, volume, balance, and fader.
3. In vehicles equipped with Premium Bose (Y91 / UQA): If the overall volume is too low, use the adjustment dial on the side of the interface to set it to the desired level. The best way to do this is to turn the volume on the radio to 3/4 volume, then turn the

adjustment dial on the OS-2X clockwise until some distortion is heard, then counter-clockwise a little.

1. If you have installed a steering wheel interface verify that all SWC buttons are functioning properly for both the aftermarket radio and OnStar. To adjust OnStar volume, press the OnStar button on the mirror then use the volume buttons on the SWC, or the adjustment dial on the side of the module to adjust the level. When you hear a chime during this process it means you have reached the farthest minimum / maximum level.

2. Pressing the OnStar button on the rearview mirror will turn off the rear speakers and allow the OnStar audio to be heard in the two front speakers. The OnStar active LED will also turn on. When OnStar disconnects, the radio will un-mute or turn back on and the OnStar LED will turn off. Pressing the VR / OnStar butto

3. Turn off vehicle and remove key. RAP will be active and keep the radio on for 10 minutes or until any door is opened.

4. The LED and radio will turn off when RAP turns off or until any door is opened

5. Use the 4-position selector switch located on the side of the CMX chime module to select the best chime output volume for your specific installation. Setting 1 being loudest and 4 being softest.

graph TD
    A["CMX chime module"] --> B["2-pin electrical component"]
    B --> C["Terminal block"]

OnStar Volume Adjustment for Vehicles without SWC

• If SWC buttons are not present use the adjustment dial on the side of the interface to control the OnStar audio level during an OnStar connection.
• When OnStar is active pressing the switch will change the audio level 10 steps.

Rear Seat Entertainment (RSE); If equipped

The factory RSE system will function independently from the aftermarket radio. The unit will power up and pass audio through the headphones as long as the vehicle's ignition is on. If you wish to pass audio from the RSE to the aftermarket radio you must connect the RCAs from the 12-pin connector to the aftermarket radios auxiliary input. Select the aftermarket radios auxiliary input to hear RSE audio.

RadioPRO PC App

Firmware Updates

The RadioPRO PC app will allow you to update the interface with new firmware as it becomes available.

Please visit https://pac-audio.com/firmware-updates/ for available updates.

Connect the interface to your PC and select "Firmware", then "Update Firmware". Now select "Select File". Finally, browse to the place where you saved the file and select it. This will begin the updating process. Once finished, disconnect the interface from the PC and test operation.

Technical Support

Email: [e-mail]

Toll Free: 866-931-8021

Standard / International: 727-592-5991