This bulletin applies to 2017-2018 Buick LaCrosse vehicles. The SES light may be on. DTC P0446 may be stored. 

Owners of 2016-2018 Buick Regal vehicles may comment that the MIL is on. DTC P0172 (fuel trim system rich) may be set in the ECM. 

This bulletin applies to all 2013-2018 Buick and other GM models. When diagnosing multiple DTCs, one of which includes U****Byte 71, any control module may set a DTC for one of its inputs, and that data is shared across the communication bus for other modules to do their respective functions. 

Some owners of 2016 Buick LaCrosse vehicles may comment about a hard brake pedal on a cold start-up and/or a service brake assist message.