Buick Regal: DTC B123E

Diagnostic Instructions

• Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic System Check - Vehicle
• Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis
• An overview of each diagnostic category can be found here: Diagnostic Procedure Instructions

DTC Descriptor

DTC B123E

Radio Keypad Button Signal Circuit

Symptom Byte Information: Symptom Byte List.

Diagnostic Fault Information

1. Radio Control buttons inoperative

Circuit/System Description

The radio controls communicate radio control inputs directly to the radio through a discrete circuit for volume up, volume down and power button. It also uses a series of resistors through a signal circuit when the home, seek up, seek down and phone buttons are pressed. After receiving the message the radio will perform the requested function. Messages communicated between the radio and the radio controls include the following:

• Button presses/knob rotations
• Commands for the state of indicators
• Controls back-lighting

Conditions for Running the DTC

• Vehicle in Service Mode/Ignition is ON or in the ACC position
• The system voltage is 9 - 16 V
• The infotainment system is ON
• The test is run once every 250 ms when the infotainment system is operating

Conditions for Setting the DTC

B123E 01

The radio detects an open/high resistance or short to voltage on the radio controls key signal circuit

B123E 02

The radio detects a short to ground on the radio controls key signal circuit

Actions Taken When the DTC Sets

Radio control buttons will be inoperative

Conditions for Clearing the DTC

The condition for setting the DTC is no longer detected for 250 ms.

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

Circuit/System Verification

1. Ignition On/vehicle in Service Mode.

2. Verify that each button on the A22 radio controls operates normally by pressing each button individually.

• If none of the buttons operate normally

Refer to Circuit/System Testing

• If some, but not all, of the buttons operate normally

Test or replace the A22 radio controls

• Go to next step: If all of the buttons operate normally

3. All OK.

Circuit/System Testing

1. Ignition OFF/vehicle OFF and all vehicle systems OFF. Disconnect the harness connector at the A22 radio controls. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 10 Ω between the following circuits and ground.

• Ground return terminal 2
• Low reference terminal 8
• If 10 Ω of greater

1. Ignition OFF/vehicle OFF, disconnect the X1 harness connector at the P17 Info Display Module.
2. 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 P17 Info Display Module

• Go to next step: If less than 10 Ω

3. Ignition ON/vehicle in Service Mode.

4. Test for 2.5 - 3.5 V on the signal circuit terminal 3 @ the A 22 Radio Controls and ground.

• If less than 2.5 V

1. Ignition OFF/vehicle OFF, disconnect the X1 harness connector at the A11 Radio.
2. Test for infinite resistance between the signal circuit and ground.
   • If less than infinite resistance, repair the short to ground.
   • 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 A11 Radio.

• If greater than 3.5 V

1. Ignition OFF/vehicle OFF, disconnect the X1 harness connector at the A11 Radio.
2. Ignition ON/vehicle in Service Mode, 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.
   • If less than 1 V, replace the A11 radio.

• Go to next step: If between 2.5 - 3.5 V

5. Test or replace the A22 Radio Controls.

Repair Instructions

• For control module replacement, programming, and setup refer to: Control Module References.

  Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification.

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