C1391 on Toyota
Abnormal Leak of Accumulator Pressure (manufacturer-specific)
C1391 on Toyota vehicles indicates abnormal leak of accumulator pressure (manufacturer-specific). Au7o has documented this code across 3 Toyota models — most commonly on 4Runner, Camry, Highlander. C1391 is a manufacturer-specific brake code, documented mainly on Toyota and Lexus (often hybrid) models, indicating the brake control system detected an abnormal leak or loss of accumulator pressure in the hydraulic ABS/brake actuator. The accumulator stores pressurized brake fluid the system uses for power-assisted and ABS braking, and degraded internal seals can let it bleed down. Because this directly affects braking assist and can increase stopping distance, it is a serious fault that should be repaired promptly by a qualified shop. Typical repair costs on Toyota range from $1,200 to $3,500, depending on the specific model and root cause.
Common Causes of C1391
- •Failing brake booster / master cylinder accumulator seals
- •Worn or leaking brake actuator assembly
- •Internal hydraulic leak in the ABS/brake actuator
- •Low brake fluid level
- •Aged or contaminated brake fluid
- •Faulty pump or pressure sensor within the actuator
- •Faulty brake control (skid control) ECU
C1391 on Toyota by Model
Toyota 4Runner(2 issues)
- ABS Actuator / Master Cylinder Assembly Failure Triggering ABS/VSC/TRAC Lights and Brake Pump Noise2003-2009
On 4th-gen 4Runners the integrated ABS actuator/brake master cylinder assembly (with electric pump motor and accumulator) fails internally. The pump motor or accumulator wears out so the pump never reaches pressure and runs continuously; owners get simultaneous ABS, BRAKE, VSC and TRAC warning lights, a loud continuous in-cabin alarm, electronic noise when braking, and a hard or sinking pedal with reduced assist. It is a safety-relevant failure and the assembly is one of the most expensive non-drivetrain parts on the truck. This is distinct from the brake booster/master-cylinder internal-leak issue: this is the ABS hydraulic actuator/accumulator unit.
- Brake Booster / Master Cylinder Internal Leak Causing Hard Pedal and Reduced Braking Assist2003-2009
Multiple 4th-generation 4Runner owners report the brake pedal becoming hard, requiring excessive effort to stop, often accompanied by ABS/VSC/TRAC warning lights and a buzzing or continuously running brake actuator. Toyota issued service information for brake booster pump/master cylinder concerns on related platforms, and owner complaints frequently describe internal accumulator or actuator failure rather than simple pad/rotor wear. Repairs are expensive because the booster/master/actuator assembly is typically replaced as a unit.
Toyota Camry(1 issue)
- Camry Hybrid Brake-Booster Internal Leak - T-SB-0130-19 / CSP ZKK2012-2014
Toyota T-SB-0130-19 and Customer Support Program ZKK apply to certain 2012-2014 Camry Hybrid vehicles with brake, ABS and/or TRAC warning lights or a Check VSC message. Verification requires C1391, C1252, C1256 or C1253. Toyota attributes the specified condition to a small internal brake-fluid leak in the brake-booster assembly with master cylinder. Warning lamps can have other causes, and the documents do not support extending this record to gasoline Camrys or other model years. ZKK's primary coverage ended March 31, 2021; its secondary coverage was 10 years or 150,000 miles from first use, so its published coverage period has expired for this model-year range as of 2026.
Toyota Highlander(1 issue)
- Hybrid Brake Booster / ABS Actuator Assembly Failure (Accumulator Leak) — C13912006-2013
The regenerative-braking brake actuator (the integrated ABS/booster/accumulator pump module) is a known weak spot on the Highlander Hybrid. The accumulator develops an internal leak and the pump runs constantly, triggering a loud, repetitive whirring/buzzing and warning lights; in some cases brake assist is reduced, which owners describe as a serious safety concern (the same family of actuators drove early Prius brake recalls). CarComplaints documents repeated brake actuator complaints on the 2006 Highlander Hybrid, and the repair is rarely covered out of warranty.
Looking for C1391 on a different make?
View C1391 across all makes →Frequently Asked Questions
What does C1391 mean on Toyota?▼
C1391 stands for "Abnormal Leak of Accumulator Pressure (manufacturer-specific)." C1391 is a manufacturer-specific brake code, documented mainly on Toyota and Lexus (often hybrid) models, indicating the brake control system detected an abnormal leak or loss of accumulator pressure in the hydraulic ABS/brake actuator. The accumulator stores pressurized brake fluid the system uses for power-assisted and ABS braking, and degraded internal seals can let it bleed down. Because this directly affects braking assist and can increase stopping distance, it is a serious fault that should be repaired promptly by a qualified shop. On Toyota specifically, this code is documented across 3 models.
What causes C1391 on Toyota vehicles?▼
Common causes on Toyota: Failing brake booster / master cylinder accumulator seals, Worn or leaking brake actuator assembly, Internal hydraulic leak in the ABS/brake actuator, Low brake fluid level, Aged or contaminated brake fluid. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix C1391 on a Toyota?▼
Repair costs on Toyota range from $1,200 to $3,500, depending on the specific model and root cause.
Which Toyota models have C1391 documented?▼
Au7o has documented C1391 on 3 Toyota models: 4Runner, Camry, Highlander.