Owners of 2015 Colorados describe brake system failures ranging from unresponsive pedals at low speeds to complete loss of braking on highways. The most common complaint is a stiff or extremely firm brake pedal requiring excessive force to depress, often paired with a "service brake assist" warning message on the dash.
Several owners report sudden brake pedal seizure—the pedal locks up solid and won't move, forcing reliance on the emergency brake. One driver at 75 MPH had to grab the emergency brake after the pedal froze. Another owner's brake pedal went to the floor and stuck there, resulting in a collision. A third owner experienced brake pedal seizure multiple times over several years.
Failures occur across the mileage spectrum: 35,000 miles to 156,000 miles. One owner reports the problem existed from the truck's purchase as new. Diagnostics consistently point to vacuum pump failure, vacuum booster failure, vacuum sensor faults, and oil contamination inside the brake booster. One owner discovered the vehicle had no engine oil when brakes failed, linking the brake system failure to engine oil depletion—an unusual cross-system issue.
One truck had brake component defects (missing and misaligned parts) discovered after recall service work under campaign 15V278000. Repairs reported include vacuum pump replacement, brake booster replacement, and electrical system work, though some owners' vehicles were never successfully repaired.
Failure modes owners describe
Brake booster vacuum failure
Brake booster loss of vacuum due to failed vacuum pump or contamination, causing brake pedal to become stiff, firm, or unresponsive and requiring excessive force to depress.
When: 35,000 to 156,000 miles; some owners report failures starting from new vehicle
Symptoms owners cite: brake pedal extremely firm or stiff; brake pedal requires excessive force to depress; brake pedal moves slowly or not at all; brake pedal pushes foot upwards; vehicle fails to stop as intended; service brake assist warning message
Repairs/costs cited: Vacuum pump replacement, vacuum sensor replacement, brake booster replacement reported. GM bulletin 11-00-89-005 addresses oil contamination in brake booster. Costs not stated by owners.
Recalls/TSBs owners mention: Recall campaign 15V278000 (service brakes, hydraulic) prior to some failures. Manufacturer case filed in complaint #1. GM notified in complaints #4 and #7.
Brake pedal lockup or seizure
Brake pedal becomes locked in floor position or seizes up completely, preventing pedal depression or releasing after depression.
When: Low mileage (35,000) to higher mileage (156,000); some occurrences reported multiple times over several years
Symptoms owners cite: brake pedal locked to floor; brake pedal seized up and cannot be pushed; brake pedal goes to floor and will not respond
Repairs/costs cited: Power brake booster and bracket replacement reported. No cost details provided.
Recalls/TSBs owners mention: GM engineer diagnosed and repaired at manufacturer cost in complaint #9, including body damage.
Brake system failure with engine oil contamination
Loss of brakes coupled with engine oil depletion, suggesting shared failure mode between brake booster and engine oil system.
When: Unknown mileage
Symptoms owners cite: brake pedal unresponsive; service brake system warning message; engine oil low warning; no oil in engine
Repairs/costs cited: Owner used emergency brake to stop vehicle safely; no repair details provided.
Vacuum booster electrical system fault
Brake booster and associated electrical system malfunction causing stiff pedal response and check engine warning.
When: 102,000 miles
Symptoms owners cite: brake pedal stiff and failed to respond; vehicle failed to start with ignition on; check engine warning indicator illuminated
Repairs/costs cited: Vacuum booster and electrical system repair needed; vehicle not repaired by owner.
Recalls/TSBs owners mention: Manufacturer contacted, case number 8-4597870930 assigned.
Brake assembly defects post-recall service
Missing and misaligned brake components on front brakes after vehicle was serviced under recall campaign 15V278000.
When: 13,234 miles, after recall service performed
Symptoms owners cite: abnormal noise after hard braking; missing parts on passenger side brakes; misaligned parts on driver side brakes
Repairs/costs cited: Brake assembly parts repaired. Vehicle had prior service under recall 15V278000.
Recalls/TSBs owners mention: Recall campaign 15V278000 (service brakes, hydraulic) was performed prior to failure. Manufacturer was notified.
Chronic brake assist malfunction
Persistent service brake assist warning message and unresponsive brakes despite multiple diagnostic visits and parts replacement, suggesting recurring system fault.
When: From new vehicle purchase; recurring over time
Symptoms owners cite: service brake assist warning message on dash; hard brake pedal; ABS pulsation in brake pedal
Repairs/costs cited: Vacuum pump sensor replaced but problem persisted. Owner reports paying for several unnecessary parts.
Synthesized from 13 NHTSA owner complaints — unverified consumer
allegations, summarized for patterns. The verbatim filings appear below.