Cellular, Entertainment, and Navigation
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 B1446 12
- Replace Backup Power Source Voltage Above Threshold
DTC B1447 04
- Backup Power Source Open Circuit
Circuit/System Description
The backup battery provides voltage to the communication interface module (CIM), 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 or B1446 12
* 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 CIM detects that the backup battery voltage has dropped below the minimum threshold value.
B1446 12
The CIM detects that the backup battery voltage has risen above the maximum threshold value.
B1447 04
The CIM detects no voltage from the backup battery.
Action Taken When the DTC Sets
B1446 03 or B1446 12
The OnStar(R) status LED turns red.
B1447 04
* The OnStar(R) status LED turns red.
* The CIM 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 03 will clear when the CIM detects the voltage of the backup battery is above the minimum threshold value.
* A current DTC B1446 12 will clear when the CIM detects the voltage of the backup battery is below the maximum threshold value.
* A current DTC B1447 04 will clear when the CIM detects voltage from the backup battery.
* A history DTC clears after 50 malfunction-free ignition cycles.
Diagnostic Aids
Important:
* Shorting the backup battery positive voltage circuit to the backup battery ground circuit or chassis ground will activate the internal circuit protection of the backup battery, rendering the backup battery inoperable.
* DTC B1447 may set if the CIM has been incorrectly disconnected or serviced. When disconnecting the CIM, disconnect the harness connector X1 at the CIM prior to disconnecting any other harness connectors. This will ensure the backup battery is preserved when voltage is removed from the CIM.
Reference Information
Schematic Reference
OnStar Schematics (OnStar Schematics)
Connector End View Reference
Component Connector End Views (Connector Views)
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)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector X1 at the CIM.
2. Test for greater than 15.5 V between terminals 13 and 14.
• If less than specified value, test the battery backup supply voltage circuit and battery backup low reference circuit for an open/high resistance, short to ground or short to voltage. If the circuits test normal, replace the backup battery.
3. If all circuits test normal, replace the CIM.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Communication Interface Module Battery Replacement (Communication Interface Module Battery Replacement)
* Control Module References (Programming and Relearning) for CIM replacement, setup and programming