P0556 on GMC
Brake Booster Pressure Sensor Circuit Range/Performance
P0556 on GMC vehicles indicates brake booster pressure sensor circuit range/performance. Au7o has documented this code across 2 GMC models — most commonly on Sierra 1500, Yukon. The brake booster pressure sensor signal is present but out of the expected range or implausible relative to operating conditions. A range/performance fault.
Common Causes of P0556
- •Faulty brake booster pressure sensor
- •Vacuum leak at the booster or hose
- •Wiring resistance / poor connection
- •Failing vacuum source / pump
- •Faulty PCM input
P0556 on GMC by Model
GMC Sierra 1500(1 issue)
- NHTSA Recall 19V645000: Declining Vacuum Pump Output Reduces Power Brake Assist2014-2018
GM recalled 2014-2018 GMC Sierra trucks under NHTSA campaign 19V645000 because the amount of vacuum created by the vacuum pump may decrease over time. The vacuum pump is what gives the Sierra's brake pedal its power assist, so as the vacuum level drops, brake assist decreases. A Sierra owner experiences this as a pedal that takes more effort to push and a truck that needs a longer distance to come to a stop, which NHTSA states increases the risk of a crash. This is a progressive condition rather than a sudden failure - the assist fades as pump output declines. The campaign covers 3,456,719 vehicles in total across all of the GM trucks and SUVs included in the recall; that figure is campaign-wide and is not a count of Sierras.
GMC Yukon(2 issues)
- GM Recall 19V645000: EBCM Reprogram for Declining Vacuum Brake Assist2015-2018
GMC Yukons from 2015 through 2018 fall under NHTSA recall 19V645000. The defect: the amount of vacuum created by the vacuum pump may decrease over time. Less vacuum reaching the brake booster means less brake assist, so the Yukon's pedal grows stiff and the truck's stopping distance stretches out - NHTSA flags this as raising the risk of a crash. Worth distinguishing from an outright vacuum pump failure: this recall is about assist that tapers off as pump output declines, and GM's approved correction is a control-module calibration rather than a pump replacement. The 3,456,719-vehicle figure attached to this campaign is the total across every GM model included in it.
- Brake Vacuum Pump Failure Causing Hard Brake Pedal2015-2018
NHTSA campaign 19V645 covers certain 2015-2018 GMC Yukon vehicles. Vacuum-pump output can decrease over time, reducing brake assist, increasing pedal effort and extending stopping distance.
Looking for P0556 on a different make?
View P0556 across all makes →Frequently Asked Questions
What does P0556 mean on GMC?▼
P0556 stands for "Brake Booster Pressure Sensor Circuit Range/Performance." The brake booster pressure sensor signal is present but out of the expected range or implausible relative to operating conditions. A range/performance fault. On GMC specifically, this code is documented across 2 models.
What causes P0556 on GMC vehicles?▼
Common causes on GMC: Faulty brake booster pressure sensor, Vacuum leak at the booster or hose, Wiring resistance / poor connection, Failing vacuum source / pump, Faulty PCM input. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0556 on a GMC?▼
Repair costs vary widely depending on the root cause and specific GMC model.
Which GMC models have P0556 documented?▼
Au7o has documented P0556 on 2 GMC models: Sierra 1500, Yukon.