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2020 - 2021 Corvette: Service Bulletin: #21-NA-099: Speaker Noise, or Loss of Bass, or Low / No Output of Audio from Individual Speaker Channels - (Apr 23, 2021)

#21-NA-099: Speaker Noise, or Loss of Bass, or Low / No Output of Audio from Individual Speaker Channels - (Apr 23, 2021)

Subject Speaker Noise, or Loss of Bass, or Low / No Output of Audio from Individual Speaker Channels



Model Year:















Built Prior to February 16, 2021

VIN 1G1YC2D49M5104684


Involved Region or Country

United States, Canada, Mexico, Middle East, Japan

Additional Options (RPOs)

Equipped with Audio Speaker System (UQH)


Some customers may comment on any of the following audio symptoms which could be either intermittent in nature, recovering after an ignition cycle, or they could occur every ignition cycle:

  • Unexpected audio noises (example: squealing, screeching)
  • Loss of bass response
  • Low or no audio output from certain speakers

These symptoms may only exist in one or more of the following seven speaker channels:

  • Radio Front Side Door Upper Speaker – Left/Right
  • Radio Front Side Door Speaker – Left/Right
  • Radio Front Center Speaker
  • Radio Front Speaker - Instrument Panel Right
  • Radio Quarter Speaker - Left


The cause of the condition may be an issue identified in the amplifier calibration.


Reprogram the T3 Audio Amplifier. This update can occur remotely through in-vehicle prompts from the radio display. However,some customers may decline the vehicle update, or the update may be unsuccessful. Along with the vehicles mentioned above,vehicles in unconnected markets, and fleet customers may need the dealer to reprogram the amplifier with the new calibration.

Service Procedure

Note: Over the Air (OTA) updates can occur for many modules. Be sure to document and take notice of what module is being updated to ensure any OTA listed is for the condition being diagnosed and repaired.

  1. 1. Determine if the amplifier update has already been downloaded over the air (OTA) and pending installation.

    Tip: Do NOT decline OTA updates for other control modules. If the amplifier OTA is available but displays a "conditions not ideal" statement, then refer to Over The Air Description and Operation in SI.

    Important: Decline the amplifier update before proceeding with SPS programming.

    1. 1.1 On the radio, select Home —> Settings —> Update to see if an OTA update for the amplifier is already present in the vehicle and pending installation. The radio will display the following statement to indicate this is the amplifier update: "This software update improves the performance of your speakers by resolving a potential intermittent loss of audio issue. During the update process, your radio may stay on up to 5 minutes after you exit the vehicle. This is expected behavior when an update package is onboard the vehicle. Do not service your vehicle during installation."
  • If the amplifier OTA is available select Install and follow the on-screen instructions.
  • If no amplifier OTA update is available, then proceed to step 2.
  • 2. Reprogram the audio amplifier follow the SPS Programming procedure.
  • Version



    Released April 23, 2021

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