GM false alarm
This TSB applies to a number of 2011 GM vehicles including the Buick Enclave, LaCrosse, Lucerne and Regal, Cadillac CTS, DTS, Escalade and SRX, Chevy Avalanche, Camaro, Corvette, Captiva, Colorado, Cruze, Equinox, Express, HHR, Impala, Malibu, Silverado, Suburban, Tahoe and Traverse, GMC Acadia, Canyon, Savana, Sierra, Terrain, Yukon, Yukon XL, Yukon Denail and Yukon Denali XL, all equipped with OnStar (generation 9.0 and 9.1 OnStar modules manufactured by LG).
While performing diagnostics, a technician may find DTC B2455 stored as a history code in the Vehicle Communication Interface Module (VCIM) when there is no issue with the microphone. If there is no current concern with the cellular phone microphone operation, disregard this DTC and do not replace the microphone or VCIM. Microphone operation may be verified by making a Blue Button OnStar call.