P0556: How to Diagnose & Fix — Brake Booster Pressure Sensor Circuit Range/Performance
8 vehicles · 5 makes · $300-$1,800 repair
How to diagnose and fix P0556: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Chevrolet Silverado 1500 · 2019–2023
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.
Common Symptoms
- Hard brake pedal
- Service Brake Assist message
- Longer stopping distance
- Brake warning light
- ABS/traction lights on
How to Fix
Have dealer diagnose specific brake booster component failure. Brake booster assembly replacement typically required. Check for GM service campaigns or extended warranty coverage. Do not drive with reduced brake assist.
Sources for this issue (1)
Ford F-150 · 2015–2020
The vacuum pump that provides brake assist on EcoBoost F-150s can fail, resulting in a hard brake pedal and reduced braking assist. Since turbo engines don't produce intake vacuum like naturally aspirated engines, they rely on this pump.
Common Symptoms
- Hard brake pedal
- Increased stopping distance
- Brake warning light
- Whining noise from pump area
- Reduced brake assist
How to Fix
Replace vacuum pump. This is a safety-critical repair - do not drive with failed pump. Check for diagnostic codes related to brake booster. Inspect vacuum lines for leaks as well.
Sources for this issue (1)
GMC Yukon · 2015–2018
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.
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)
GMC Yukon · 2015–2018
GMC Sierra 1500 · 2014–2018
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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?
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.
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?
Repair costs for P0556 range from $300 to $1,800, depending on the vehicle and root cause.
Which vehicles are affected by P0556?
Au7o has documented P0556 across 8 vehicle models from 5 manufacturers: Cadillac, Chevrolet, Ford, GMC, Toyota.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.