Buick Regal: DTC B1277 (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 provide an overview of each diagnostic category.

DTC Descriptors

DTC B1277

Microphone 1 Input Signal Circuit

For symptom byte information refer to Symptom Byte List.

Diagnostic Fault Information

Circuit/System Description

The human machine interface control module uses the cellular telephone microphone for voice recognition and cellular features. The human machine interface control module provides a bias voltage to each microphone (+) and (-) signal circuits for operation of the microphone.

Conditions for Running the DTC

The human machine interface control module performs a self diagnostic of the microphone circuits once after initial power up.

Conditions for Setting the DTC

B1277 02

The human machine interface control module detects an short to ground in the cellular phone microphone high signal circuit.

B1277 04

The following conditions will set this DTC:

• The human machine interface control module detects an open/high resistance in the cellular phone microphone high signal circuit.
• The human machine interface control module detects an open/high resistance in the microphone low signal circuit.

Action Taken When the DTC Sets

The voice recognition system malfunctions or is inoperative.

Conditions for Clearing the DTC

• A current DTC clears when the self diagnostic passes on the next ignition cycle.
• A history DTC clears when the ignition cycle counter reaches the reset threshold without a repeat of the malfunction.

Reference Information

Schematic Reference

Radio/Navigation System Wiring Schematics (IOB) , Radio/Navigation System Wiring Schematics (IOR) or Radio/Navigation System Wiring Schematics (IO5/IO6) , or Radio/Navigation System Wiring Schematics (IOS/IOT).

Connector End View Reference

Component Connector End View Index

Description and Operation

Radio/Audio System Description and Operation (IO6) , Radio/Audio System Description and Operation (IOB) , or Radio/Audio System Description and Operation (IOS/IOT/IOU).

Electrical Information Reference

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

Scan Tool Reference

Control Module References for scan tool information.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the B24 Cellular Phone Microphone. Ignition On/Vehicle in Service Mode.

2. Test for 9 - 11 V between the signal circuit terminal B and ground.

• If less than 9 V

1. Ignition OFF, disconnect the X1 harness connector at the K74 Human Machine Interface Control Module.
2. Test for infinite resistance between the signal circuit and ground.
   • 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 signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K74 Human Machine Interface Control Module.

• If greater than 11 V

1. Ignition OFF, disconnect the X1 harness connector at the K74 Human Machine Interface Control Module. Ignition On/Vehicle in Service Mode.
2. Test for less than 1 V between the signal circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • Go to next step: If less than 1 V, replace the K74 Human Machine Interface Control Module.

• Go to next step: If between 9 - 11 V

3. Test for less than 1 V between the signal circuit terminal A and ground.

• If greater than 1 V

1. Ignition OFF, X1 harness connector at the K74 Human Machine Interface Control Module.

   Ignition On/Vehicle in Service Mode.

2. Test for less than 1 V between the signal circuit and ground.
   • If 1 V or greater, repair the short to voltage in the circuit.
   • If less than 1 V, replace the K74 Human Machine Interface Control Module.

• Go to next step: If less than 1 V

4. Ignition OFF, disconnect the X1 harness connector at the K74 Human Machine Interface Control Module.

5. Test for infinite resistance between the B24 Cellular Phone Microphone signal circuit terminal A and ground.

• If less than infinite resistance

Repair the short to ground in the circuit

• Go to next step: If infinite resistance

6. Test for less than 2 Ω in the signal circuit end to end.

• If 2 Ω or greater

Repair the open/high resistance in the circuit

• Go to next step: If less than 2 Ω

7. Replace the B24 Cellular Phone Microphone.

8. Ignition On/Vehicle in Service Mode.

9. Verify the DTC does NOT set.

• If the DTC sets

Replace the K74 Human Machine Interface Control Module

• Go to next step: If the DTC does not set

10. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Refer to Mobile Telephone Microphone Replacement
• Refer to Control Module References for human machine interface control module replacement, programming, and setup.

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