The Lemon IndexOn Toyota and Lexus models with a powered brake booster (mostly hybrids), the brake computer saw the stored brake pressure falling faster than it should, which points to an internal leak.
Stop and fix now. Don't put it off. This can affect safety, stall the car or cause expensive damage.
Internal leak in the brake booster/accumulator assembly. Then: leaking seals in the brake actuator.
Owners named C1391 in 373 complaints to the U.S. government, most often on the Toyota Prius.
Models that report it most
Complaints that name C1391, by model. Raw counts, not a failure rate: popular models get more complaints. Tap a model for its years, mileage and what owners say fixed it.
C1391 by model: C1391 Toyota Prius (210) · C1391 Toyota Highlander (49) · C1391 Toyota Camry (20)
Years owners report it on most: 2010 Toyota Prius · 2013 Toyota Prius · 2011 Toyota Prius · 2012 Toyota Prius · 2008 Toyota Highlander · 2014 Toyota Prius
The details
What C1391 means
On Toyota and Lexus models with a powered brake booster (mostly hybrids), the brake computer saw the stored brake pressure falling faster than it should, which points to an internal leak. Braking assist can be affected, so get it checked before driving much.
This meaning applies to Toyota, Lexus. On other makes C1391 can mean something different.
Can I drive with C1391?
Stop and fix now. Don't put it off. This can affect safety, stall the car or cause expensive damage.
98% of the owner complaints that name C1391 also say the car brakes or ABS act up. A complaint can describe more than one problem, so this doesn't prove the code caused it.
Common causes of C1391
- Internal leak in the brake booster/accumulator assembly
- Leaking seals in the brake actuator
A shop should confirm the cause with a scan and tests before replacing parts.
What owners describe
- Brakes or ABS act up: 98% of complaints
- Warning lights and electrical faults: 31% of complaints
- Transmission slips or shifts hard: 8% of complaints
- Loses power or goes into limp mode: 2% of complaints
Share of complaints naming the code whose text also mentions each problem.
Model years that report C1391 most
2010 Toyota Prius (61), 2013 Toyota Prius (42), 2011 Toyota Prius (30), 2012 Toyota Prius (27), 2008 Toyota Highlander (22), 2014 Toyota Prius (19).
Quick answers
What does C1391 mean?
Abnormal Leak in Brake Accumulator. On Toyota and Lexus models with a powered brake booster (mostly hybrids), the brake computer saw the stored brake pressure falling faster than it should, which points to an internal leak. Braking assist can be affected, so get it checked before driving much.
Can I drive with C1391?
Stop and fix now. Don't put it off. This can affect safety, stall the car or cause expensive damage.
What causes C1391?
Internal leak in the brake booster/accumulator assembly; Leaking seals in the brake actuator.
Counts: NHTSA owner complaints whose text names C1391. A complaint is an owner's report, not a diagnosis. Meanings: the standard SAE J2012 definitions in our own words; manufacturer codes only where verified for that make. General information, not repair advice for your car.