Conditions for Setting the DTC

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2012 GMC Yukon XL, 2012 GMC Yukon, 2012 Chevrolet Tahoe, 2012 Chevrolet Suburban, and 2012 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

No vacuum is detected in the power brake booster for approximately 10 seconds after start-up.
Low vacuum is detected in the power brake booster for approximately 60 seconds or longer after start-up, or is detected while driving.