For 1990-2009 cars

### Diagnostic Aids

• | The Global Positioning System (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.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: OnStar Schematics Connector End View Reference: Entertainment/Communication Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Important: It is important to have the vehicle in an open outside area where a cellular call can be successfully placed and Global Positioning System (GPS) data can be received from satellites. It is also necessary to inform the OnStar® Call Center advisor that this call is for vehicle diagnostic purposes.

With a scan tool, observe the GPS signal status indicator in the GPS Data Display menu, for at least 10 seconds.

Does the indicator display Yes?

--

Go to Step 3

Go to Step 6

3 |

1. Press the OnStar® Call Center button.
2. Ask the OnStar® Call Center advisor if they have received GPS data.

Has the advisor received GPS data?

--

Go to Step 4

Go to Step 5

4 | Ask the OnStar® Call Center advisor to verify your position. Is the location provided by the OnStar® Call Center advisor within a reasonable distance from the actual location of the vehicle? | -- | Go to Diagnostic Aids | Go to Step 10
5 | Ask the OnStar® Call Center advisor if this call was a fail to voice. Was the call a fail to voice? | -- | Contact the General Motors Technical Assistance Center | Go to Step 6
6 | Important: Vehicle may be equipped with sectioned coax. Test each section and replace only the faulty section, not the entire length or coax.

1. Disconnect the navigation antenna coax from the navigation antenna within the wiring harness.
2. Disconnect the navigation antenna from the vehicle communication interface module (VCIM).
3. Measure the resistance from the center conductor of the coax to the metal outer shield.

Does the meter read out of limits?

--

Go to Step 7

Go to Step 8

7 | Measure the resistance of the navigation antenna coax center conductor from end to end. Does the resistance measure greater than the specified value? | 1 ohms | Go to Step 8 | Go to Step 9
8 | Replace the navigation antenna coax. Did you complete the replacement? | -- | Go to Step 11 | --
9 | Replace the navigation antenna assembly. Refer to Cellular and Navigation Antenna Assembly Replacement . Did you complete the replacement? | -- | Go to Step 11 | --
10 | Replace the VCIM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 11 | --
11 | Operate the system in order to verify the repair. Did you correct the condition? | -- | Go to Step 2 | --