Skip to content
Tahoe / Yukon Service Manual

DTC B15A1

Cellular, Entertainment, and Navigation | Diagnostic Information and Procedures | Document ID: 5198495 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. DTC Descriptors DTC B15A1 Telematics Speaker (+) For symptom byte information refer to Symptom Byte List. Diagnostic Fault Information

Circuit number Circuit Function Short to Ground Open/High Resistance Short to Voltage Signal Performan
4770 Control B15A1 11 B15A1 13 — —

Circuit/System Description The K73 Telematics Control Module utilizes the vehicles infotainment systems speaker to broadcast audio in the case of emergency road assistance. In the event the infotainment system becomes inoperable there is an P50 Regulatory Emergency Call Backup Speaker connected directly to the K73 Telematics Control Module. Each of the audio output channel circuits (+) and (-), at the K73  Telematics Control Module have a DC bias voltage that is approximately one half of battery voltage. When using a DMM, each of the audio output channel circuits will measure approximately 6.5 V DC. The audio being played on the system is produced by a varying AC voltage that is centered around the DC bias voltage on the same circuit. The AC voltage is what causes the speaker cone to move and produce sound. The frequency (Hz) of the AC voltage signal is directly related to the frequency of the input. Both the DC bias voltage and the AC voltage signals are needed for the system to properly produce sound. Conditions for Running the DTC Ignition ON/vehicle in service mode The system voltage is 9-16 V The test is run once every 10 s Conditions for Setting the DTC B15A1 11 The K73 Telematics Control Module detects a short to ground on the audio signal (+) circuit. B15A1 13 The K73 Telematics Control Module detects an open on the audio signal (+) circuit. Action Taken When the DTC Sets The red LED status indicator is illuminated. Conditions for Clearing the DTC Conditions for Clearing the DTC A current DTC clears when the conditions for setting the DTC are no longer present and the ignition has been cycled from OFF to ON. A history DTC clears after 100 malfunction-free ignition cycles. Reference Information Schematic Reference OnStar/Telematics Schematics Connector End View Reference Master Electrical Component List Description and Operation OnStar Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References for scan tool information Circuit/System Testing

  1. Ignition/vehicle OFF and all vehicle systems Off, disconnect the harness connector at the P50 Regulatory Emergency Call Backup Speaker. Ignition ON/vehicle in service mode.
  2. Test for 5–7 V between the audio control circuit terminal 2 and ground. ⇒ If less than 5 V 2.1. Ignition/vehicle OFF, disconnect the harness connector X1 at the K73 Telematics Control Module. 2.2. Test circuit 4770 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 2.3. Test circuit 4770 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit or ground connection ⇒ If an open/high resistance is not found. Replace the K73 Telematics Control Module ⇒ If greater than 7 V 2.1. Ignition/vehicle OFF, disconnect the harness connector X1 at the K73 Communication Interface Module. Ignition ON/vehicle in service mode. 2.2. Test circuit 4770 for a short to voltage. ⇒ If a short to voltage is found repair the fault on the circuit. ⇒ If no short to voltage is found, replace the K73 Telematics Control Module. ⇓ If between 5–7 V
  3. Test or replace the P50 Regulatory Emergency Call Backup Speaker. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Control Module References for programming and setup.