Buick Regal: DTC B127C
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 B127C 02
Microphone 2 Input Signal Circuit Short to Ground
DTC B127C 04
Microphone 2 Input Signal Circuit Open/High Resistance
Diagnostic Fault Information
Circuit/System Description
The radio provides the microphone 2 with a supplied voltage on the microphone
high signal circuit.
When the microphone is in use, voice data from the user is sent back to the
radio on the microphone low
signal circuit. This microphone is used for driver side hands free calling
enhancement, as well as a
reference microphone for the primary microphone.
Conditions for Running the DTC
- The ignition must be in the RUN or ACC position/vehicle in Service Mode.
- The system voltage is at least 9.5 V and no more than 15.5 V.
- All the above conditions are present for greater than 5 s.
Conditions for Setting the DTC
B127C 02
The radio detects a short to ground in the microphone high signal circuit for
5 s or greater.
B127C 04
The following conditions will set this DTC:
- The radio detects an open/high resistance in the microphone high signal
circuit for 10 s or greater.
- The radio detects an open/high resistance in the microphone low signal
circuit for 10 s or greater.
Action Taken When the DTC Sets
- The radio will not receive a signal from the microphone.
Conditions for Clearing the DTC
- The condition responsible for setting the DTC no longer exists.
- A history DTC will clear once 50 consecutive malfunction-free ignition
cycles have occurred.
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/vehicle 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 2 and ground.
- Ignition OFF/vehicle OFF, disconnect the X1 harness connector at the A11
Radio.
- 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
- 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 A11 Radio.
- Ignition OFF/vehicle OFF, disconnect the X1 harness connector at the A11
Radio.
- 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 A11 Radio.
- Go to next step: If between 9-11 V
3. Test for less than 1 V between the low reference circuit terminal 1 and
ground.
- Ignition OFF/vehicle OFF, disconnect the X1 harness connector at the A11
Radio.
- Test for less than 1 V between the low reference circuit and ground.
- If 1 V or greater, repair the short to voltage in the circuit.
- If less than 1 V, replace the A11 Radio
- Go to next step: If less than 1 V
4. Test for greater than 9 V between the signal circuit terminal 2 and the
low reference circuit
terminal 1.
- Ignition OFF/vehicle OFF, disconnect the X1 harness connector at the A11
Radio.
- Test for infinite resistance between the low reference circuit and
ground.
- If less than infinite resistance, repair the short to ground in the
circuit.
- Go to next step: If infinite resistance
- 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 A11 Radio.
- Go to next step: If greater than 9 V
5. Test or replace the B24 Cellular Phone Microphone.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
- Refer to Mobile Telephone Microphone Replacement
- Refer to Control Module References for telematics communication
interface control module
replacement, programming and setup.
READ NEXT:
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.
Refe
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.
Refe
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.
Refe
SEE MORE:
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.
Diagnostic Procedure Instructions provides an overview of each
diagnostic category.
Diagnostic Fault
SPECIFICATIONS
APPROXIMATE FLUID CAPACITIES
FLUID AND LUBRICANT RECOMMENDATIONS
MAINTENANCE ITEMS
MAINTENANCE REPLACEMENT PARTS
Replacement parts identified below by name, part number, or specification can
be obtained from your
dealer.
MAINTENANCE
MAINTENANCE SCHEDULE
The Maintenance Schedule