P0556 on Chevrolet

Third-generation Equinox (2018-2022) uses a camshaft-driven mechanical vacuum pump mounted at the rear of the cylinder head to supply the brake booster (the turbo intake is pressurized, so there is no manifold vacuum). This pump can seize and its drive gear break, suddenly eliminating brake assist — the pedal becomes 'hard as a rock' with greatly increased stopping distances. In severe cases the pump shatters and sends metal debris into the engine, causing catastrophic internal damage. NHTSA has over 300 complaints; a related GM recall (19V645000) reprogrammed the brake control module on other models but excluded the Equinox/Terrain, and a February 2026 class action (Thieme v. General Motors) targets 2018-2022 Equinox/Terrain.

The T1 generation Silverado can experience brake assist malfunctions, causing a hard brake pedal, longer stopping distances, and warning lights. The electric brake booster or its sensors may be the cause.

The engine-driven brake vacuum pump on 2014-2018 Silverado 1500 trucks (5.3L and 6.2L V8) can lose vacuum output over time as oil sludge and debris are trapped by the pump's oil inlet filter screen. As vacuum drops, power brake assist decreases, producing a hard brake pedal, increased pedal effort, and longer stopping distances, most noticeably at low speed (parking lots, slowing for crosswalks). GM recalled roughly 3.4 million trucks and SUVs for this condition under NHTSA campaign 19V645000 (GM recall N192268490), and NHTSA's underlying investigation was closed after the recall.

2015-2018 Chevrolet Suburbans are covered by GM safety recall 19V645000. GM determined the vacuum produced by the vacuum pump may decrease over time, and the brake booster depends on that vacuum to do most of the work of applying the brakes. On a vehicle as heavy as the Suburban, losing assist matters: NHTSA states that as the vacuum level drops, braking effort increases and the distance required to stop the vehicle extends, raising crash risk. The condition builds gradually, so it is easy to adapt to a stiffening pedal without recognizing it as a defect. The recall's 3,456,719 units affected is a campaign-wide total covering all the GM trucks and SUVs named in it.