For 1990-2009 cars

### Circuit Description

The cellular antenna is connected to the vehicle communication interface module (VCIM) with a RG-58 coax cable. The VCIM polls the data from the cellular antenna once every second.

### Conditions for Running the DTC

• | The ignition must be in the RUN or ACC position.

• | The system voltage is at least 9.5 volts and no more than 15.5 volts.

• | All the above conditions are present for greater than 1 second.

### Conditions for Setting the DTC

• | The VCIM does not detect the presence of a cellular antenna.

• | All the above conditions are present for greater than 1 second.

### Action Taken When the DTC Sets

• | The OnStar® status LED turns RED.

• | The vehicle is unable to connect to the OnStar® Call Center.

### Conditions for Clearing the DTC

• | The VCIM detects the presence of a cellular antenna.

• | A history DTC clears after 50 malfunction-free ignition cycles.

• | The VCIM receives the clear DTC command from the scan tool.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step tests the condition of the Cellular Antenna.

2. This step tests the condition of the cellular antenna coax and for proper ground of the cellular antenna.

Step | Action | Value | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: OnStar Schematics Connector End View Reference: Cellular Communication Connector End Views
1 | Did you perform the Cellular Communications Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check - Cellular Communication
2 | Inspect the cellular antenna and cellular antenna coupling assembly for damage. Is the antenna assembly damaged? | -- | Go to Step 7 | Go to Step 3
3 |

1. Disconnect the cellular antenna coax from the vehicle communication interface module (VCIM).
2. Measure the resistance between the center conductor and the outer metal shield.

Does the meter read out of limits?

--

Go to Step 4

Go to Step 5

4 |

1. Disconnect the cellular antenna coax from the VCIM.
2. Measure the resistance of the cellular antenna coax connector from end to end.

Does the resistance measure greater than the specified value?

1 ohms

Go to Step 8

Go to Step 6

5 | Inspect for poor connections at the harness connector of the VCIM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9
6 | Inspect for poor connections at the harness connector of the cellular antenna. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7
7 | Replace the cellular antenna. Refer to Mobile Telephone Antenna Inner Coupling Replacement and Mobile Telephone Antenna Outer Coupling Replacement . Did you complete the replacement? | -- | Go to Step 10 | --
8 | Replace the cellular antenna coax. Did you complete the replacement? | -- | Go to Step 10 | --
9 | Replace the VCIM. Refer to Communication Interface Module Replacement . Did you complete the replacement? | -- | Go to Step 10 | --
10 |

1. Use the scan tool in order to clear the DTCs.
2. Operate the vehicle within the conditions for running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK