B1447

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

Circuit/System Description

The backup power source 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
* 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 power source voltage has dropped below the minimum threshold value.

B1447 04

The CIM 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 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 will clear when the CIM detects the voltage of the backup power source is above the minimum threshold value.
* A current DTC B1447 will clear when the CIM detects voltage from the backup power source.
* A history DTC clears after 50 malfunction-free ignition cycles.

Diagnostic Aids

Important:
* 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 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 power source 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 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, 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 B+ circuit and low reference circuit for an open/high resistance, short to ground or short to voltage. If the circuits test normal, replace the backup power source.

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