This Preliminary Information communication advises the technician that the Hydro-Boost is not serviceable and will need to be replaced if the brake pedal moves or applies on its own at a full turn.
full bulletin at NHTSA ↗2015 GMC Sierra brakes problems
severe 207 complaints filed with NHTSA · avg repair $450 · see brakes across all vehicles →
Failure mileage
Complaints
207
Recalls
0
Avg fix
$450
14crashes
1fire
2injuries
When does it fail?
Of the 207 brakes complaints filed for the 2015 GMC Sierra, here's the actual mileage breakdown — failures cluster heaviest at 50,000-75,000 mi.
0-25k
25-50k
50-75k
75-100k
100-125k
125-150k
150k+
Each bar shows the share of total complaints filed at that mileage range. Peak failure window highlighted. Some owners report problems earlier; some make it well past 150,000 miles symptom-free. Maintenance habits and driving conditions shift the curve as much as mileage alone.
What stands out
Of the 19 model years of GMC Sierra we track for brakes problems, this one carries the most owner complaints on file — 207.
Owners have filed 207 brakes complaints with NHTSA against this vehicle, but no formal recall covers the issue — the federal record reflects what manufacturers have admitted, not everything owners are reporting.
Is there a fix? Manufacturer service bulletins
The manufacturer has issued service bulletins covering brakes on this vehicle — documented repair instructions, service campaigns, or warranty extensions sent to dealers. A TSB isn't a recall (it's not a free safety remedy), but it's the manufacturer acknowledging the issue and how to fix it.
GENERAL MOTORS: PARTS FOR MOST VEHICLES, CLUTCH, MASTER CYLINDER ASSEMBLY ARE, REQUIRED AND REQUESTED, TO BE RETURNED AND NEED TO REORDER REPLACEMENT PARTS USING SAME PART NUMBERS.
full bulletin at NHTSA ↗This Preliminary Information communication provides information to the technician about vehicles that are equipped with 6L80 Regular Production Option Code (MYC), 6L90 Regular Production Option Code (MYD) or 8L90 Regular Production Option Code (M5U) Automatic Transmission. Starting with the 2013 model year, Full Size Trucks and Utilities now have Powertrain Grade Braking. Powertrain grade braking assists when driving on a downhill grade to help maintain desired vehicle speed by using the engine and transmission to slow the vehicle.
full bulletin at NHTSA ↗This Preliminary Information communication provides information to the technician with the steps on diagnosing and repairing vehicles that may have unwanted grade braking, reduced engine power with no Driver Information Center messages ? Brake Pedal Override Feature ?, transmission busy or frequent shifting up or down, and Diagnostic Trouble Codes P057B, P057C, and/or P057D may or may not be set. Technician will use this preliminary information to find the brake pedal position data parameters in the scan tool, and also to provide some additional diagnostic help. These issues may be caused by an incorrect brake pedal position sensor input to the engine control module. Technician will verify w
full bulletin at NHTSA ↗This Preliminary Information communication provides information to the technician with the steps on diagnosing and repairing vehicles that may have unwanted grade braking, reduced engine power with no Driver Information Center messages "Brake Pedal Override Feature", transmission busy or frequent shifting up or down. Technician will use this preliminary information to find the brake pedal position data parameters in the scan tool, and also to provide some additional diagnostic help. These issues may be caused by an incorrect brake pedal position sensor input to the engine control module. Technician will verify with the scan tool if the engine control module has the correct parameters for the
full bulletin at NHTSA ↗Source: NHTSA manufacturer communications. Bring the bulletin number to your dealer or shop.
The failure pattern owners describe
Owners describe brake failures primarily at low speeds (under 10 mph)—parking, reversing, creeping traffic. The brake pedal suddenly becomes rock hard and unresponsive, or sometimes goes soft to the floor with zero stopping power. No warning lights precede these failures. Owners report hitting curbs, parked vehicles, concrete barriers, and family members' cars while unable to stop. The problem is intermittent but reproducible: it triggers repeatedly under low-speed conditions, sometimes within days of each other.
Dealerships blame a faulty vacuum pump that loses function and eliminates brake boost. Owners cite GM NHTSA Campaign 19V645000 and a "special policy" on vacuum pump failures, but many report the repair—usually pump or booster replacement—either fails to fix the problem or the failure recurs. At mileage over 72,000 miles, GM often denies coverage despite the vehicle still being within original ownership.
A secondary group reports progressive brake stiffening during stop-and-go traffic on downhill grades: after the first stop, each successive brake application makes the pedal stiffer until it barely moves, leaving the truck unable to prevent roll-forward. One owner documented oil contamination from the pump into brake fluid. A third group reports the trailer brake controller shutting down under load, leaving 14,000-pound trailers with zero braking and no manual override. Owners across forums note this is not isolated—multiple 2014–2018 GM trucks share the problem.
Same GMC Sierra brakes reports on nearby years: 2014 · 2017 · 2018
Failure modes owners describe
Brake pedal loss of boost/assist at low speeds
Brake pedal becomes extremely stiff and unresponsive during low-speed driving (parking, reversing, stop-and-go traffic, creeping). Pedal may travel to the floor without providing braking force or resist depression with extreme hardness. Loss of brake assist is intermittent but reproducible under low-speed conditions.
When: Typically occurs below 10 mph during parking, reversing, or slow-speed city driving; mileage range 38,000–110,000 miles
Symptoms owners cite: Extremely stiff or hard brake pedal; Brake pedal travels to floor with no stopping power; Pedal resists depression and pushes back against driver; Vehicle fails to stop or requires excessive force on pedal; Loss of brake boost/power assist; Intermittent and reproducible at low speeds; Engine running and foot off brake, brake pedal falls to floor; Ticking or moaning noise from brake booster area
Repairs/costs cited: Vacuum pump replacement; brake booster replacement; master cylinder replacement; brake fluid, hoses, and related components (costs cited: $686–$1,800 for full repair including pump, booster, cylinder, and pipes)
Recalls/TSBs owners mention: NHTSA Campaign 19V645000 (Service Brakes, Hydraulic) issued; some owners report recall repair failed or worsened the condition; GM extended special policy for vacuum pump failures on certain model years but limited by mileage thresholds (72,000 miles cited); some owners reported GM denied coverage at higher mileage
Brake pedal stiffening during repeated low-speed braking
After coming to a stop or reaching low speed, brake pedal progressively stiffens with each successive brake application, eventually reducing to minimal travel (~1 inch) and insufficient braking force to prevent vehicle roll on downhill grades.
When: During stop-and-go traffic, downhill traffic lights, successive parking maneuvers; mileage range 47,000–80,000 miles
Symptoms owners cite: Brake pedal stiffens progressively with repeated braking; Pedal travel reduces to roughly 1 inch after multiple applications; Braking force barely sufficient to prevent idle roll-forward; Vehicle fails to stop adequately on downslopes; Requires massive pedal pressure to prevent rear-end collision; Difficulty stopping after coming to initial stop
Repairs/costs cited: Vacuum pump failure confirmed; pump replacement resolves symptom
Complete brake failure at low speed (no stopping power)
Sudden, catastrophic loss of all braking power during low-speed operations (parking, reversing, slow traffic). Brake pedal either goes soft/to floor or becomes rock hard with zero response. No gradual degradation; failure occurs without warning lights or diagnostic codes.
When: Low speeds (under 10 mph), parking lots, reversing, slow traffic; mileage range 34,000–85,500 miles; some incidents occur within months of recall repair
Symptoms owners cite: Complete loss of braking power at low speed; No warning lights or messages before failure; Vehicle continues moving forward or backward despite pedal depression; Brake pedal either extremely soft or rock hard; Multiple collisions with parked vehicles, curbs, concrete barriers, neighboring vehicles reported; Crashes at 2–10 mph speed range; Problem reproducible at dealership; Failure occurs without prior warning
Repairs/costs cited: Multiple brake system component replacements including vacuum pump, booster, master cylinder; some owners report recurring failures even after pump replacement; crash repair costs $22,000 documented in one case
Recalls/TSBs owners mention: NHTSA Campaign 19V645000; GM special policy on vacuum pump failures; some dealers unable to diagnose without active fault codes; some dealers replaced vacuum pump multiple times with continued failures
Trailer brake controller malfunction and loss of trailer braking
Brake controller shuts down power to trailer brakes intermittently, triggered by minor deviations in trailer brake wiring resistance (1 ohm or less). 'Check Trailer Wiring' message displays repeatedly; controller lacks failsafe override. Affects heavy trailers (14,000+ lbs) with no backup braking.
When: Intermittent, occurring for 6 months or longer; affects towed vehicles with trailers
Symptoms owners cite: Repeated 'Check Trailer Wiring' warning message; Brake controller shuts off power to trailer brakes; Complete loss of trailer braking ability; No manual override available to restore trailer brakes; Unsafe condition when towing heavy cargo; Highly sensitive controller triggers shutdown on minor wiring deviations
Repairs/costs cited: Controller upgrade/replacement attempted; brake wiring inspected; issue persists after dealer and trailer shop repairs
Recalls/TSBs owners mention: Dealer informed that 2014+ models have upgraded, more sensitive controller; no successful remedy reported by owners
Trailer brake warning system false alerts and wiring harness defect
Defective factory wiring harness in trailer brake warning system causes repeated 'Trailer Brake Warning' service light and loud beeping during normal driving. Warning persists even after repair attempts. Makes vehicle undrivable during episodes; interferes with hands-free phone system and navigation display.
When: During cross-country road trips and regular driving; incidents during extreme heat exposure; warning occurs intermittently and persistently (50+ times per incident reported)
Symptoms owners cite: Trailer Brake Warning service light illuminates; Loud, continuous beeping (50+ times per incident documented); Hands-free phone system becomes inoperable; Navigation system covered by warning display; Periodic illumination and flashing of warning; Vehicle becomes undrivable during episodes; Requires engine restart attempts to reset warning without success
Repairs/costs cited: Fuse replacement; wiring harness check; defective harness preserved for inspection; repeated repair costs ($150 in 2019, $465 in 2022 plus car rental $80); total out-of-pocket $695
Recalls/TSBs owners mention: No recall issued; GMC made no effort to address; owners reported no response from manufacturer
Brake booster and hydraulic ABS control unit failure
Brake booster fails along with hydraulic ABS control unit, causing front brake calipers to lock up and fail to release. No warning lights illuminate until booster is replaced. Extensive parts replacement required; ticking noise from engine noted post-repair.
When: Early in vehicle ownership (within 3 days of purchase reported); continuing intermittently thereafter
Symptoms owners cite: Front brake calipers lock up and do not release; Vehicle difficult to control during braking; No warning lights (ABS light only illuminates after booster replacement, indicating ABS control unit also bad); Ticking noise from engine at idle and during throttle activation; Brakes lock up unpredictably
Repairs/costs cited: Two sets of calipers, two sets of brake pads, one set of rotors, brake master cylinder, brake booster, hydraulic ABS control unit replaced; two-week diagnosis and repair period
Recalls/TSBs owners mention: Dealer declined to explain ticking noise or provide information on cause post-repair
Brake antilock system (ABS) failure during low-speed parking
Antilock system underperforms during low-speed parking and maneuvering in residential areas and parking lots. Brakes take longer to engage and lack control feel; system works normally at highway speeds.
When: Low-speed parking and reversing; normal function at expressway speeds; ongoing after recall service
Symptoms owners cite: Prolonged brake response during low-speed stops; Loss of vehicle control feel during parking; Antilock system does not function properly in parking scenarios; Normal function at highway speeds; Fear of collision or crash due to control loss
Repairs/costs cited: Owner took truck to certified mechanic who confirmed brakes fine; concluded antilock system at fault; owner also had recall service at dealer with no improvement
Recalls/TSBs owners mention: Recall service performed at Luke Fruia GMC, Brownsville, TX with no resolution of problem
Brake master cylinder and booster leaks
Brake booster and master cylinder develop leaks, resulting in loss of brake pressure and reduced braking ability at low speeds.
When: Around 46,000 miles
Symptoms owners cite: Very difficult to stop truck at low speeds (5–10 mph); Excessive stopping distance required; Brakes do not become fully functional until vehicle is placed in park, shut down, and left 15 minutes before restarting; After brake restoration, vehicle operates normally
Repairs/costs cited: Leaking brake booster and master cylinder identified
Brake pedal stiffness with intermittent loss of braking on downhill grades
Brake pedal becomes stiff and hard, particularly on downhill driving and when backing trailers down ramps. Intermittent loss of effective braking force despite pedal pressure application.
When: When backing boats/trailers down ramps on grades; intermittent occurrence over years of ownership
Symptoms owners cite: Hard brake pedal requiring excessive force; Reduced braking effectiveness on downhill grades; Difficulty stopping when backing boat trailers down ramps; Intermittent but reproducible under specific load and grade conditions; Requires emergency brake use as workaround
Repairs/costs cited: Not yet diagnosed by dealer at time of complaint
Brake fluid contamination from vacuum pump oil
Engine oil from the vacuum pump contaminates the brake system fluid, causing system malfunction and reduced braking performance.
When: Several incidents over approximately one week during boat launching and farm gate operations
Symptoms owners cite: Brakes require pump action (multiple brake pedal presses) to stop vehicle; Light brake touch does not stop immediately as expected; Vehicle travels further than anticipated before stopping (6–8 feet overshoot); Braking failure on slight hill declines
Repairs/costs cited: Vacuum pump, booster, cylinder, pipe, and fluid replaced; total cost $1,266.33
Synthesized from 207 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 4 most recent
4 months ago the display portrayed a message stating, trailer brake warning, have system checked. Since that time I have attempted on numerous to have my vehicle checked. But as of this date I have not been to have any dealership look at my vehicle. I have been told by dealership that the vehicle computer shows a history but no current error codes, and they can not work on vehicle until it has…
It started happening a week or so ago where when in reverse or after switching from reverse to drive and trying to brake the pedal wouldn't compress, it was as if they were locking up on me. I would have to put most of my body weight on the pedal to even get the truck to stop, to the point where I almost ran into my neighbors car backing out of the driveway. It seemed to mainly happen at slower…
Service Trailer Brake Brake System error keeps flashing.
Brake pump went out almost ran into a pole. Reading online and see a lot of people having the same problem. Angry!!
Had brakes trouble with your 2015 GMC Sierra?
File a complaint with NHTSA → It's free, official, and how every report above got here — owner filings are the federal safety record this page is built on.
Common questions
How serious is the brakes problem on the 2015 GMC Sierra?
It's a meaningful issue. 207 complaints have been filed and the failure mode causes operational problems for owners. Repairs average $450.
At what mileage does the brakes typically fail?
Across the 157 complaints that reported odometer mileage, most brakes failures cluster between 43,000 and 75,000 miles, with the median around 56,000. A quarter of owners report trouble before 43,000; a quarter make it past 75,000. Maintenance history matters more than the odometer alone — this is the reported failure window, not a guarantee.
What does it cost to fix?
Independent shops typically charge around $450 for brakes repairs on this vehicle. Dealer pricing tends to run 20-40% higher. The exact figure depends on the specific failure mode, parts availability, and your local labor rates. If you're outside factory warranty, an extended service contract often covers this category.
Are there any recalls related to brakes?
No active recalls currently cover brakes issues on this vehicle. The complaints filed represent owner-reported failures that haven't risen to the level of a manufacturer-issued recall — but they're still worth knowing about before you buy or budget for repairs.
Related
Complaint and recall data sourced from the National Highway Traffic Safety Administration (NHTSA)
public records database. Verify the raw federal record at
nhtsa.gov/vehicle/2015/GMC/Sierra.
Severity ratings are derived from reported crashes, fires, injuries, and fatalities. Repair cost estimates are
independent-shop national averages and may differ in your area. Some links on this page are affiliate links.