P0556 on GMC: How to Diagnose & Fix
Brake Booster Pressure Sensor Circuit Range/Performance
1 GMC model · 2 documented issues · 2 critical
P0556 on GMC by model: symptoms, diagnosis and fix
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)
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.
Call to confirm they can assess your vehicle and perform the stated work. Search results do not confirm qualification, eligibility or coverage.
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 1 model: 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.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.