P0556: How to Diagnose & Fix — Brake Booster Pressure Sensor Circuit Range/Performance
6 vehicles · 4 makes · $400-$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 2019-and-later Silverado can experience brake assist malfunctions, causing a hard brake pedal, longer stopping distances, and warning lights. GM documents a Brake System Control Module (EBCM) software calibration fault on 2019 trucks (PIT5638B, and recall 20V-055 for faulty pre-launch EBCM software) that can disable brake assist and set a Service Brake Assist message.
Common Symptoms
- Hard brake pedal
- Service Brake Assist message
- Longer stopping distance
- Brake warning light
- ABS/traction lights on
How to Fix
Have a dealer diagnose the brake assist fault. On 2019 trucks, check recall 20V-055 and bulletin PIT5638B; the fix is reprogramming the Brake System Control Module, not booster replacement. Check for GM service campaigns or extended warranty coverage. Do not drive with reduced brake assist.
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 (2)
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.
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)
Chevrolet Suburban · 2015–2018
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 covers about 3.5 million GM trucks and SUVs (3,456,719 vehicles).
Common Symptoms
- Increased brake pedal effort
- Longer stopping distances
- Weakening power brake assist over time
How to Fix
The fix is free at a Chevrolet dealer and takes the form of a software update - the dealer reprograms the Electronic Brake Control Module. GM began owner notification October 8, 2019; the internal campaign number is N192268490. Enter your Suburban's VIN at nhtsa.gov/recalls to confirm whether this recall is still open, then contact Chevrolet customer service at 1-800-630-2438 or your local dealer to have the reprogramming performed.
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)
Chevrolet Silverado 1500 · 2014–2018
GMC Yukon · 2015–2018
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P0556 code reference
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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 $400 to $1,800, depending on the vehicle and root cause.
Which vehicles are affected by P0556?
Au7o has documented P0556 across 6 vehicle models from 4 manufacturers: Cadillac, Chevrolet, GMC, Toyota.
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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.