Buick Regal: DTC B1446 or B1447 (IOR/IOS/IOT)

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Refer to Diagnostic Procedure Instructions for 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. The backup power source is under an access cover on the telematics communication interface control module.

Conditions for Running the DTC

B1446

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

B1447

• 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.

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. 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.

B1447 04

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

Action Taken When the DTC Sets

B1446

The OnStar status LED turns red.

B1447

• 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.

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. This will take 10 consecutive ignition cycles to run the DTC pass/fail tests.
• 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.

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 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 s 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.

Reference Information

Schematic Reference

OnStar/Telematics Wiring Schematics

Connector End View Reference

Component Connector End View Index

Description and Operation

OnStar Description and Operation (UE1 with IOB/IO6) , OnStar Description and Operation (UI3) , or OnStar Description and Operation (UE1 without IOB/IO6).

Electrical Information Reference

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

Circuit/System Verification

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.

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

     Test or replace the K73 Telematics Communication Interface Control Module

   • Go to next step: If DTC B1446/B1447 is not set.

     Go to next step: All OK.

• Go to next step: If DTC B1446/B1447 is not set

2. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Refer to Communication Interface Module Battery Replacement (IO5, IO6, IOB) or Communication Interface Module Battery Replacement (IOR, IOS, IOT)
• Refer to Control Module References for telematics communication interface control module replacement, programming and setup.

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