Diagnostic Instructions
Circuit/System Description
The communication interface module (CIM) receives information from a specific navigation antenna located on the outside of the vehicle. The navigation antenna is connected to the CIM via a shielded coaxial cable. The antenna cable also provides a path
for DC current for powering the antenna.
Diagnostic Aids
| • | The GPS signal title on the scan tool will display a Yes or No dependant upon whether or not the module sees an increment of the seconds transmitted by GPS signals to the vehicle communication interface module. Upon entering this screen, the GPS
signal title will automatically display Yes, regardless of the presence of time increment, for at least 2 seconds, while the algorithm in the scan tool determines the status of the clock. If increment is found, Yes is continually displayed. If the clock
remains static, No is displayed. The scan tool looks for increment every second, regardless of current display. |
| • | Inaccurate or aged GPS position concerns which are no longer present may have been due to the temporary loss of GPS signal reception by the vehicle. Conditions such as driving through tunnels or parking structures while making an OnStar® keypress
will restrict the navigation antenna from a clear view of the satellites in the sky and may have caused this temporary data loss. |
Reference Information
Schematic Reference
OnStar Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
OnStar Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Important: It is important to have the vehicle in an open outside area where a cellular call can be successfully placed and GPS data can be received from the satellites. It is also necessary to inform the OnStar® Call Center
advisor that this call is for vehicle diagnostic purposes.
- Ignition ON, observe the GPS signal status indicator for at least 10 seconds with a scan tool. The indicator should display Yes.
| ⇒ | If the indicator does not display Yes, refer to Circuit/System Testing. |
- Call and verify the OnStar advisor has received the GPS data.
| ⇒ | If the advisor did not receive the GPS data and the call was a "fail to voice", contact the GM Technical Assistance Center. |
| ⇒ | If the advisor did not receive the GPS data and the call was not a "fail to voice", refer to Circuit/System Testing. |
- Verify with the OnStar Call Center advisor that your actual position is within a reasonable distance from the actual location of the vehicle.
| ⇒ | If your actual position is not within a reasonable distance from the actual location of the vehicle, replace the CIM. |
Circuit/System Testing
- Disconnect the navigation antenna coax cable from the CIM.
- Ignition ON, test for 4.5-5.5 V between the CIM coax cable center conductor terminal at the module and ground.
| ⇒ | If not within the specified range, replace the CIM. |
- Reconnect the coax cable to the CIM. Disconnect the coax cable from the navigation antenna.
- Test for 4.5-5.5 V between the coax cable center conductor and the outer shield.
| ⇒ | If not within the specified range, replace the coax cable. |
- If all circuits test normal, replace the navigation antenna.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
