B1327

DTC B1327

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 Descriptor
DTC B1327
- Device Voltage Circuit Low

Diagnostic Fault Information





Circuit/System Description

The control modules on this vehicle monitor system voltage through the battery positive voltage circuits. Damage to components, and incorrect data can occur when the voltage is out of range. The following modules can set DTC B1327:

* Digital radio receiver (DRR)
* Radio
* Vehicle communications interface module (VCIM)

Conditions for Running the DTC

* The module has power and ground.
* The ignition switch is not in START.
* When the vehicle exits START, the module will delay checking the voltage for 2 seconds.

Conditions for Setting the DTC

The control module detects that the battery voltage is less than 9.5 V for 1.2 seconds

Action Taken When the DTC Sets

* A serial data message will be sent to notify all other modules of low battery voltage.
* The module disables the setting of other DTCs.

Conditions for Clearing the DTC

* The DTC will pass when the voltage is greater than 9.5 V for 1.2 seconds.
* A history DTC will clear after 50 consecutive ignition cycles, if the condition for the malfunction is no longer present.

Diagnostic Aids

A high or low voltage DTC in multiple modules indicates a concern with the charging system.

Reference Information
Schematic Reference

* Radio/Navigation System Schematics (Radio/Navigation System Schematics)
* OnStar Schematics (OnStar Schematics)

Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

Charging System Description and Operation (Description and Operation)
Electrical Information Reference

* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Circuit Testing (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Testing

1. Engine running, accessories OFF, measure and record the battery voltage at the battery terminals. The voltage should be between 12.6 and 15.0 V.

• If not within the specified range, refer to Charging System Test (Component Tests and General Diagnostics).

2. Ignition OFF, disconnect the harness connectors at the appropriate module.
3. Ignition OFF and scan tool disconnected, open and close the driver door, and wait 30 seconds. Test for less than 5 Ohms between the appropriate ground circuit terminals listed below and ground.

* Terminal 9 (DRR)
* Terminal A12 X1 (Radio)
* Terminal B5 X1 (Radio)
* Terminal 7 X1 (VCIM)

• If greater than the specified range, test the ground circuit for an open/high resistance.

4. Verify that a test lamp illuminates between the appropriate B+ circuit terminal listed below and ground.

* Terminal 16 (DRR)
* Terminal B1 X1 (Radio)
* Terminal 16 X1 (VCIM)

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

5. If all circuits test normal, replace the appropriate module.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

Control Module References (Programming and Relearning) for the appropriate module replacement, setup, and programming.