• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

The backup power source provides voltage to the telematics communication interface control module, to be able to successfully place a call in the event of a main battery disconnect during a collision event. The backup power source is under an access cover on the telematics communication interface control module.

• Vehicle is ON.
• System voltage is between 9.5 and 15.5 V.
• DTC B1447 is not set.

• Vehicle is ON.
• System voltage is between 9.5 and 15.5 V.
• The above conditions are present for greater than 10 s.
• DTC B1446 is not set.

The telematics communication interface control module detects that the backup power source voltage has dropped below the minimum threshold value. Threshold voltage is checked once every ignition On cycle. There is a counter in memory which counts the number of passes and fails. On the first fail the DTC sets as current. The counter must record 10 consecutive passes before the DTC current status clears. This counter carries over across ignition On/Off cycles.

The telematics communication interface control module detects no voltage from the backup power source. Voltage is checked every 10 m during ignition On cycle

The telematics communication interface control module detects voltage above the threshold from the backup power source.

The telematics communication interface control module detects temperature above the threshold from the backup power source.

The OnStar® status LED turns red.

• The OnStar® status LED turns red.
• The telematics communication interface control module will be unable to place a call in the event of a main battery disconnect during a collision event.

• A current DTC B1446 will clear when the telematics communication interface control module detects the voltage of the backup power source is above the minimum threshold value. This may take up to 10 consecutive ignition cycles to run the DTC pass/fail test.
• A current DTC B1447 will clear when the telematics communication interface control module detects voltage from the backup power source. Voltage is checked every 10 m during ignition On cycle.
• A history DTC clears after 40 malfunction-free ignition cycles.

• Shorting the backup power source positive voltage circuit to the backup power source ground circuit or chassis ground will activate the internal circuit protection of the backup power source, rendering the backup power source inoperative.
• DTC B1447 may set if the K73 Telematics Communication Interface Control Module has been incorrectly disconnected or serviced. When the backup power source mode is enabled due to a loss of vehicle battery power the K73 Telematics Communication Interface Control Module will wait 10 seconds before placing an emergency call. If an emergency call is deemed not necessary the K73 Telematics Communication Interface Control Module will disconnect the C3 Telematics Communication Interface Control Module Battery preventing the discharge of the backup power source.

OnStar/Telematics Schematics

Master Electrical Component List

OnStar Description and Operation

• Testing for Intermittent Conditions and Poor Connections
• Circuit Testing
• Wiring Repairs
• Connector Repairs

1. Verify DTC B1446/B1447 is not set.
• If DTC B1446/B1447 is set

  Test or replace the C3 Telematics Communication Interface Control Module Battery.

2. Verify DTC B1446/B1447 is not set.
• If DTC B1446/B1447 is set

  Test or replace the K73 Telematics Communication Interface Control Module

• If DTC B1446/B1447 is not set
3. All OK.

Perform the Diagnostic Repair Verification after completing the repair.

• Communication Interface Module Battery Replacement
• Control Module References for telematics communication interface control module replacement, programming and setup.