1. Introduction
The Axxess GMOS-05 OnStar Interface is designed to facilitate the replacement of an Original Equipment Manufacturer (OEM) radio with an aftermarket receiver in specific non-amplified GM vehicles. This interface is compatible with vehicles equipped with the "Door-n-Lock" style harness. It ensures the retention of key factory features, including OnStar functionality and safety/warning chimes, while also providing necessary outputs for navigation radio installations.
2. Safety Information
Please read all instructions carefully before installation. Improper installation may result in damage to the vehicle's electrical system, the interface module, or the aftermarket radio.
- Disconnect the vehicle's negative battery terminal before beginning any installation.
- Ensure all connections are secure and properly insulated to prevent short circuits.
- Consult a professional car audio installer if you are unsure about any part of the installation process.
- This product contains chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. Wash hands after handling.
3. Package Contents
Verify that all items are present before proceeding with the installation.
- Axxess GMOS-05 Interface Module
- Main Wiring Harness (with "Door-n-Lock" style connector)
- Secondary Wiring Harness (for power/ground/speaker connections)
4. Setup and Installation
This section provides general instructions for installing the GMOS-05 interface. Specific vehicle disassembly and reassembly procedures are not covered and should be referenced from a vehicle-specific service manual or professional guide.
4.1. Wiring Connections
Match the wires from the GMOS-05 harness to the corresponding wires on your aftermarket radio's harness. Refer to the color codes below.
| Wire Color | Function | Connect To |
|---|---|---|
| Yellow | 12V Constant Power | Aftermarket Radio Yellow Wire |
| Red | 12V Accessory Power | Aftermarket Radio Red Wire |
| Black | Ground | Aftermarket Radio Black Wire |
| Orange | Illumination | Aftermarket Radio Orange Wire (if applicable) |
| Blue/White | Amplifier Turn-On | Aftermarket Radio Amp Turn-On Wire (if applicable) |
| Green | Left Front Speaker (+) | Aftermarket Radio Left Front Speaker (+) |
| Green/Black | Left Front Speaker (-) | Aftermarket Radio Left Front Speaker (-) |
| White | Right Front Speaker (+) | Aftermarket Radio Right Front Speaker (+) |
| White/Black | Right Front Speaker (-) | Aftermarket Radio Right Front Speaker (-) |
| Gray | Left Rear Speaker (+) | Aftermarket Radio Left Rear Speaker (+) |
| Gray/Black | Left Rear Speaker (-) | Aftermarket Radio Left Rear Speaker (-) |
| Violet | Right Rear Speaker (+) | Aftermarket Radio Right Rear Speaker (+) |
| Violet/Black | Right Rear Speaker (-) | Aftermarket Radio Right Rear Speaker (-) |
| Light Green | Parking Brake Output | Aftermarket Radio Parking Brake Input (for navigation) |
| Blue | Vehicle Speed Sense (VSS) Output | Aftermarket Radio VSS Input (for navigation) |
| Brown | Reverse Output | Aftermarket Radio Reverse Input (for navigation/camera) |
Note: This wiring diagram is a general guide. Always refer to the specific wiring instructions provided with your aftermarket radio and vehicle for precise connections.
4.2. Installation Steps
- Prepare Vehicle: Disconnect the negative battery terminal. Remove the factory radio from the dashboard.
- Wire Connections: Connect the wires from the GMOS-05 harness to the aftermarket radio harness according to the wiring color code (Section 4.1). Solder and heat-shrink all connections for reliability.
- Connect GMOS-05 Module: Plug the prepared GMOS-05 harness into the GMOS-05 interface module.
- Vehicle Connection: Connect the vehicle-specific connectors from the GMOS-05 harness into the factory wiring harnesses in the vehicle's radio opening.
- Navigation Outputs: If installing a navigation radio, connect the Light Green (Parking Brake), Blue (VSS), and Brown (Reverse) wires from the GMOS-05 harness to the corresponding inputs on your navigation radio.
- Test System: Before reassembling the dashboard, reconnect the vehicle's negative battery terminal. Turn on the ignition and test the aftermarket radio, OnStar, and safety chimes.
- Adjust Settings: Adjust OnStar volume and chime levels as described in Section 5.1.
- Final Assembly: Once all functions are verified, securely mount the aftermarket radio and reassemble the dashboard.
5. Operating Features and Adjustments
The GMOS-05 interface retains several factory features and allows for adjustments to optimize your audio experience.
5.1. OnStar and Chime Volume Adjustment
The GMOS-05 allows for independent adjustment of OnStar volume and safety/warning chime levels. This is typically done via potentiometers (small adjustment screws) located on the GMOS-05 module itself.
- OnStar Volume: Locate the potentiometer labeled "OnStar Vol" or similar on the module. Use a small screwdriver to turn clockwise to increase volume, counter-clockwise to decrease.
- Chime Volume: Locate the potentiometer labeled "Chime Vol" or similar. Adjust as needed to ensure safety chimes are audible but not overly loud.
Perform these adjustments with the vehicle running and the aftermarket radio powered on to accurately gauge the sound levels.
5.2. Navigation Radio Outputs
The GMOS-05 provides dedicated outputs for aftermarket navigation radios, which require specific vehicle data for proper operation.
- Parking Brake Output: Signals when the parking brake is engaged, often required by navigation units for certain functions.
- Vehicle Speed Sense (VSS) Output: Provides vehicle speed data for accurate navigation tracking.
- Reverse Output: Activates when the vehicle is in reverse, useful for aftermarket backup cameras or navigation features.
6. Maintenance
The Axxess GMOS-05 interface module is designed for maintenance-free operation once properly installed.
- Ensure all wiring connections remain secure and free from corrosion.
- Avoid exposing the module to extreme temperatures or moisture.
- Do not attempt to open or modify the module, as this will void the warranty.
7. Troubleshooting
| Problem | Possible Cause | Solution |
|---|---|---|
| No audio from aftermarket radio. | Incorrect speaker wiring; no power to radio; interface not initialized. | Verify all speaker wires are correctly connected. Check 12V constant and accessory power. Ensure the interface is properly connected to the vehicle's data bus. |
| OnStar or safety chimes are not working or are too loud/quiet. | Incorrect connection to GMOS-05; volume potentiometers need adjustment. | Confirm the GMOS-05 module is properly connected. Adjust the "OnStar Vol" and "Chime Vol" potentiometers on the module (refer to Section 5.1). |
| Aftermarket radio does not power on. | No 12V constant or accessory power; blown fuse. | Check the vehicle's fuse box for blown fuses. Verify the Yellow (constant) and Red (accessory) wires are correctly connected and receiving power. |
| Navigation features (e.g., parking brake, VSS, reverse) are not functioning. | Outputs from GMOS-05 not connected to navigation radio. | Ensure the Light Green, Blue, and Brown wires from the GMOS-05 are correctly connected to the corresponding inputs on your navigation radio (refer to Section 4.1). |
If troubleshooting steps do not resolve the issue, contact Axxess technical support or a certified installer.
8. Specifications
- Model: GMOS-05
- Brand: Axxess
- Manufacturer: Metra Electronics
- Compatibility: Non-amplified GM Vehicles with "Door-n-Lock" style harness (2000-2005 models)
- Material: Copper, Polyvinyl Chloride (PVC)
- Dimensions (L x W x H): 7 x 1.8 x 5 inches
- Weight: 8 ounces
- UPC: 086429126484
- Features: Retains OnStar, Retains Safety/Warning Chimes, Provides Navigation Outputs (Parking Brake, VSS, Reverse)
9. Warranty and Support
The Axxess GMOS-05 interface is manufactured by Metra Electronics. For warranty claims or technical support, please contact the retailer from whom the product was purchased. The retailer will then coordinate with Metra Electronics for warranty services. It is recommended to retain your proof of purchase for warranty purposes.
For additional technical assistance or detailed product information, please visit the official Axxess or Metra Electronics website.
