This bulletin applies to 2017-2020 Buick Envision vehicles equipped with am LCV engine. The SES (service engine soon) and/or the Service Brake Assist message may be illuminated and DTC P0557 may be set.

The cause of the condition may be inconsistent in-rush current provided by the 5V reference during the start/stop crank event. Replace the power brake booster vacuum pipe with the later version. This contains a sensor that is more robust against in-rush variation during the start/stop crank events. The updated vacuum pipe assembly is P/N 84974396.