This bulletin applies to 2015-2021 Chevy Colorado and GMC Canyon trucks. The brake booster may have a vacuum leak, possible audible hiss noise and/or DTC C0299 stored. The cause may be due to the vacuum pump leaking oil into the booster.
If you confirm that the brake booster is leaking, inspect inside the vacuum hose and booster for a sticky substance on the rubber. If present, this is likely an indication that the vacuum pump is leaking oil. Replace the pump and hose along with the booster if needed.