P0556 on GMC: How to Diagnose & Fix
Brake Booster Pressure Sensor Circuit Range/Performance
2 GMC models · 3 documented issues · 3 critical
P0556 on GMC by model: symptoms, diagnosis and fix
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.
Common Symptoms
- Increased effort required to push the brake pedal
- Longer distance needed to stop the truck
- Brake assist that weakens gradually over time
How to Fix
The remedy is free at any GMC dealer: the dealer reprograms the Electronic Brake Control Module (EBCM). No brake hardware replacement is part of the recall remedy. GM began notifying owners October 8, 2019, and GM's internal number for the campaign is N192268490. If you bought your Sierra used or never received a letter, enter your VIN at nhtsa.gov/recalls to see whether this recall is still open on your truck, then call GMC customer service at 1-800-462-8782 or your dealer to schedule the reprogramming.
Sources for this issue (1)
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.
Common Symptoms
- Harder brake pedal / more pedal effort needed
- Extended stopping distance
- Gradual loss of power brake assist
How to Fix
Take the Yukon to a GMC dealer, who will reprogram the Electronic Brake Control Module free of charge - a calibration update, no parts required. Owner notification started October 8, 2019 under GM number N192268490. Verify your VIN at nhtsa.gov/recalls before assuming it was already done, especially on a used Yukon, and call GMC customer service at 1-800-462-8782 or your dealer to set an appointment.
Sources for this issue (1)
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.
Common Symptoms
- Harder brake pedal
- Increased stopping distance as vacuum assist decreases
How to Fix
Check the VIN with GMC or NHTSA. Dealers reprogram the electronic brake-control module free of charge under GM recall N192268490.
Sources for this issue (1)
P0556 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0556 mean on a 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 it is documented across 2 models: Sierra 1500, Yukon.
What are the most common causes of P0556?
The most common causes of P0556 are: Faulty brake booster pressure sensor, Vacuum leak at the booster or hose, Wiring resistance / poor connection, Failing vacuum source / pump, Faulty PCM input. The specific cause varies by vehicle.
How much does it cost to fix P0556 on a GMC?
Repair costs vary widely with the root cause and GMC model; each issue on this page carries its own estimate where one is published.
Looking for P0556 on a different make?
View P0556 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.