B1446
DTC B1446 or B1447
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC B1446 03
- Replace Backup Power Source Voltage Below Threshold
DTC B1447 04
- Backup Power Source Open Circuit
Diagnostic Fault Information
Circuit/System Description
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.
Conditions for Running the DTC
B1446 03
* Ignition is in the RUN or ACC position.
* System voltage is between 9.5 and 15.5 V.
* DTC B1447 is not set.
B1447 04
* Ignition is in the RUN or ACC position.
* System voltage is between 9.5 and 15.5 V.
* The above conditions are present for greater than 10 seconds.
Conditions for Setting the DTC
B1446 03
The telematics communication interface control module detects that the backup power source voltage has dropped below the minimum threshold value.
B1447 04
The telematics communication interface control module detects no voltage from the backup power source.
Action Taken When the DTC Sets
B1446 03
The OnStar(R) status LED turns red.
B1447 04
* The OnStar(R) 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.
Conditions for Clearing the DTC
* 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.
* A current DTC B1447 will clear when the telematics communication interface control module detects voltage from the backup power source.
* A history DTC clears after 50 malfunction-free ignition cycles.
Diagnostic Aids
* 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 inoperable.
* DTC B1447 may set if the K73 telematics communication interface control module has been incorrectly disconnected or serviced. When disconnecting the K73 telematics communication interface control module, disconnect the harness connector X1 at the K73 telematics communication interface control module prior to disconnecting any other harness connectors. This will ensure the backup power source is preserved when voltage is removed from the K73 telematics communication interface control module.
Reference Information
Schematic Reference
OnStar Schematics OnStar Schematics
Connector End View Reference
Component Connector End Views Connector End Views By Name
Description and Operation
OnStar Description and Operation OnStar
Electrical Information Reference
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Circuit Testing Circuit Testing
* Wiring Repairs Wiring Repairs
* Connector Repairs Connector Repairs
Circuit/System Testing
1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the C3 telematics communication interface control module battery. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohms between the low reference circuit terminal B and ground.
• If 10 ohms or greater
1. Ignition OFF, disconnect the X1 harness connector at the K73 telematics communication interface control module.
2. Test for less than 2 ohms in the low reference circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K73 telematics communication interface control module.
• If less than 10 ohms
Note: The following step features a component test of the C3 telematics communication interface control module battery. It measures the voltage level of the C3 telematics communication interface control module battery.
3. Test for 15.5 V or less between the battery positive voltage circuit terminal A and low reference terminal B.
• If greater than 15.5 V
1. Ignition OFF, disconnect the X1 harness connector at the K73 telematics communication interface control module.
2. Test for infinite resistance between the battery positive voltage circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the battery positive voltage circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K73 telematics communication interface control module.
• If 15.5 V or less
4. Test or replace the C3 telematics communication interface control module battery.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Communication Interface Module Battery Replacement Communication Interface Module Battery Replacement
* Control Module References Programming and Relearning for telematics communication interface control module replacement, programming and setup.