Buick Regal: DTC B1446 or B1447 (IOB/IO5/IO6)

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

Replace Backup Power Source Below Minimum Threshold

DTC B1447

Backup Power Source Open Circuit

For symptom byte information refer to Symptom Byte List

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 On/Vehicle in Service Mode.
• System voltage is between 9.5 and 15.5 V.
• DTC B1447 is not set.

B1447 04

• Ignition On/Vehicle in Service Mode.
• System voltage is between 9.5 and 15.5 V.
• The above conditions are present for greater than 10 s.

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 status LED turns red.

B1447 04

• 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.
• 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 inoperative.
• 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/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 Testing

1. Ignition OFF/Vehicle OFF and all vehicle systems OFF, disconnect the X1 harness connector at the K73 Telematics Communication Interface Control Module. It may take up to 2 minutes for all vehicle systems to power down.

2. Test for greater than 12.3 V between the B+ circuit terminal 14 and the low reference circuit terminal 13.

• If 12.3 V or less

1. Disconnect the C3 Telematics Communication Interface Control Module Battery.
2. Test for infinite resistance between the circuits listed below and ground.
   • B+ circuit terminal 14
   • Low reference circuit terminal 13.
     • If less than infinite resistance, repair the short to ground in the circuit.
     • Go to next step: If infinite resistance.
3. Test for less than 2 Ω in the circuits end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the C3 Telematics Communication Interface Control Module Battery.

• Go to next step: If greater than 12.3 V

3. Replace the K73 Telematics Communication Interface Control Module.

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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