2010 Cadillac CTS Sedan AWD V6-3.6L Page 181
Radio/Audio System Description and Operation (See: Accessories and Optional Equipment/Description and Operation/Radio/Audio System
Description and Operation)
Electrical Information Reference
* Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/Circuit Testing/Circuit Testing)
* Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/Connector Repairs/Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics/Circuit
Testing/Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/Wiring Repairs/Wiring Repairs)
Special Tools
EL-48028 Digital Radio Test Antenna
Circuit System Verification
With the vehicle outside in an area with an unobstructed view of the southern sky, tune to XM. Verify XM reception is clear and the No XM Signal
message is not displayed on the radio.
Circuit/System Testing
1. Ignition OFF, disconnect the disconnect the digital radio antenna coax from the radio. Connect the EL-48028 to the radio and place on the
roof of the vehicle.
2. Ignition ON, radio tuned to XM channel 1. Verify DTC B125C is not set as current and XM reception is improved.
瀚慖f DTC B125C is set as current or the reception is not improved, replace the radio.
3. Ignition OFF, reconnect the antenna coax cable at the radio. Disconnect the antenna coax cable from the digital radio antenna.
4. Ignition ON, radio ON, test for 4.5-5.5 V between the antenna coax cable center terminal and an outer shield.
瀚慖f less than the specified range, test the antenna coax cable for an open/high resistance.
瀚慖f greater than the specified range, test the antenna coax cable for a short to voltage.
5. If all circuits test normal, replace the digital radio antenna.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* Digital Radio, Mobile Telephone, and Vehicle Location Base Replacement (See: Accessories and Optional Equipment/Service and Repair)
* Control Module References (See: Testing and Inspection/Programming and Relearning) for radio replacement, setup, and programming
B128A
DTC B128A
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC B128A 01
- Mono Audio Signal Circuit Short to Battery
DTC B128A 02
- Mono Audio Signal Circuit Short to Ground
Circuit/System Description
When a OnStar(R) key press is made, a serial data message is sent to the audio system to mute all radio functions and transmit OnStar(R) originated
audio. After the audio is muted, the OnStar(R) signals are transmitted to the audio system on the mono audio signal out circuit, and returned to the
module on the mono audio signal in circuit.
