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Tahoe / Yukon Service Manual

DTC B1A99 or B1A9A

Cellular, Entertainment, and Navigation | Diagnostic Information and Procedures | Document ID: 5398047 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 provide an overview of each diagnostic category. DTC Descriptors DTC B1A99 Left/Rear Subwoofer Speaker DTC B1A9A Right Subwoofer Speaker For symptom byte information refer to Symptom Byte List. Diagnostic Fault Information

Circuit Circuit Function Short to Ground Open/High Resistance Short to Voltage Signal Performan
346 Signal B1A99 11 B1A99 13 B1A99 12 B1A99 2B
1794 Signal B1A99 11 B1A99 13 B1A99 12 B1A99 2B
1795 Signal B1A9A 11 B1A9A 13 B1A9A 12 B1A9A 2B
315 Signal B1A9A 11 B1A9A 13 B1A9A 12 B1A9A 2B

Circuit/System Description The audio amplifier is a participant on the Ethernet bus. The audio amplifier receives audio signals and control information from the Radio. The Amplifier receives battery power and ground from the vehicle harness, and also communicates on GMLAN Each of the audio output channel circuits (+) and (−), at the audio amplifier have a DC bias voltage that is approximately one half of the battery voltage. When using a DMM, each of the audio output channel circuits will measure approximately 6.5V 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. Diagnostic Aids Improper speaker mounting or loose trim may cause an audible buzz or distortion. Inspect the appropriate speaker and the surrounding interior trim for proper and secure mounting. The EL-50334-6 Audio System Diagnostic CD contains audio tracks that can be used to duplicate and isolate such concerns. Tracks 11 and 12 contain audio sweep tones for testing for speaker and grill rattles. If the speaker or surrounding interior trim is found to be loose or improperly secured, correctly secure the item. The test tones on the CD may be copied to a USB drive or other device to use during testing. Some audio output circuits are connected to more than one speaker, dependant on vehicle equipment. It may be necessary to disconnect one or more speakers during testing of some circuits. Conditions for Running the DTC DTC U3006, U3007, U3008, or U3009 is not set. B1A99 11, B1A9A 11 The test is run initially upon amplifier wake-up, and periodically every one second after amplifier operation begins. B1A99 12, B1A9A 12 The test is run initially upon amplifier wake-up, and periodically every one second after amplifier operation begins. B1A99 13, B1A9A 13 The test is run once during amplifier wake-up. Conditions for Setting the DTC B1A99 11, B1A9A 11 A short to ground is detected on the specified (+) or (−) signal circuit B1A99 12, B1A9A 12 A short to voltage is detected on the specified (+) or (−) signal circuit B1A99 13, B1A9A 13 An open is detected on the specified (+) or (−) signal circuit Action Taken When the DTC Sets The amplifier mutes the output channel and no sound is present from the speaker(s) that have a current circuit fault. Conditions for Clearing the DTC The condition for setting the DTC is no longer present. A history DTC will clear once 50 consecutive malfunction-free ignition cycles have occurred. Reference Information Schematic Reference Radio/Navigation System Schematics Connector End View Reference Master Electrical Component List 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 Special Tools EL-50334-50 USB Cable and Adapter Kit Circuit/System Verification

  1. Ignition ON/Vehicle in Service Mode. Infotainment system ON, mute OFF.
  2. Verify clear audio is heard from each speaker, adjusting fade and balance controls to test each speaker individually. ⇒ If audio is inoperative from one or more speakers, or the audio emitted is not clear Refer to Circuit/System Testing. ⇓ If clear audio is heard from all speakers
  3. All OK. A fault is currently not present and may be an intermittent condition. Circuit/System Testing FTB 11, 12, 13, 2B
  1. Ignition OFF, disconnect the appropriate P19 Speaker(s): DTC B1A99 = P19 Speaker(s) connected to circuit 346 DTC B1A9A = P19 Speaker(s) connected to circuit 1795
  2. Ignition ON, infotainment system ON, mute OFF.
  3. Test for 5-7 V between the signal circuit terminal 2 and ground. ⇒ If less than 5 V 3.1. Test the appropriate circuit for a short to ground: DTC B1A99 = Circuit 346 DTC B1A9A = Circuit 1795 ⇒ If a short to ground is found, repair the circuit fault. ⇓ If a short to ground is not found 3.2. Test the appropriate circuit for an open/high resistance: DTC B1A99 = Circuit 346 DTC B1A9A = Circuit 1795 ⇒ If an open/high resistance is found, repair the circuit fault. ⇓ If an open/high resistance is not found 3.3. Replace the T3 Audio Amplifier ⇒ If greater than 7 V 3.1. Test the appropriate circuit for a short to voltage: DTC B1A99 = Circuit 346 DTC B1A9A = Circuit 1795 ⇒ If a short to voltage is found, repair the circuit fault. ⇓ If a short to voltage is not found 3.2. Replace the T3 Audio Amplifier ⇓ If between 5-7 V
  4. Test for 5-7 V between the signal circuit terminal 1 and ground. ⇒ If less than 5 V 4.1. Test the appropriate circuit for a short to ground: DTC B1A99 = Circuit 1794 DTC B1A9A = Circuit 315 ⇒ If a short to ground is found, repair the circuit fault. ⇓ If a short to ground is not found 4.2. Test the appropriate circuit for an open/high resistance: DTC B1A99 = Circuit 1794 DTC B1A9A = Circuit 315 ⇒ If an open/high resistance is found, repair the circuit fault. ⇓ If an open/high resistance is not found 4.3. Replace the T3 Audio Amplifier ⇒ If greater than 7 V 4.1. Test the appropriate circuit for a short to voltage: DTC B1A99 = Circuit 1794 DTC B1A9A = Circuit 315 ⇒ If a short to voltage is found, repair the circuit fault. ⇓ If a short to voltage is not found 4.2. Replace the T3 Audio Amplifier ⇓ If between 5-7 V
  5. Disconnect the appropriate harness connector at the T3 Audio Amplifier
  6. Test for infinite resistance between signal circuit terminal 1 and signal circuit terminal 2 at the appropriate P19 Speaker. ⇒ If less than infinite resistance Repair the short between the two signal circuits. ⇓ If infinite resistance
  7. Replace the appropriate P19 Speaker. FTB 28
  8. Ignition ON/Vehicle in Service Mode. Infotainment system ON, mute OFF.
  9. Verify that none of the DTCs listed below are set: DTC B1A99 2B DTC B1A9A 2B ⇒ If the DTC is set 2.1. Clear the DTC. 2.2. Infotainment system ON, mute OFF. 2.3. Verify the DTC does not reset. ⇒ If the DTC resets, replace the T3 Audio Amplifier ⇓ If the DTC does not reset 2.4. All OK. ⇓ If the DTC is not set
  10. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Speaker Replacement Reference Control Module References for audio amplifier replacement, programming, and setup.