C1391Brake accumulator leak detected

• Toyota/Lexus code · ABS / stability control
• Lights a warning lamp

How the car detects it

The skid control unit sees the accumulator pressure falling when it should hold steady, which points to fluid leaking inside the brake booster or actuator. Toyota has run support programs that cover the brake booster and pump on some hybrids (for example 2015-2017 Prius c and 2014-2016 Highlander Hybrid), using this code as proof. Braking still works, but the brake assist may be reduced and the pedal can feel different. If the red brake warning light is on, have the car checked before driving further.

What you may notice

• Brake, ABS and/or VSC warning lights
• Pump running more often or longer than usual

Likely causes

• PossibleInternal leak in the brake booster / actuator
• RareExternal brake-fluid leak

Sources

• static.nhtsa.gov › MC-10109482-9999.pdf · official document
• toyota-club.net › br_ecb_6d.htm
• static.nhtsa.gov › MC-10158575-9999.pdf · official document
• static.nhtsa.gov › MC-11011632-0001.pdf · official document

Backed by an official manufacturer document.

From Obdaryn's Toyota/Lexus pack, exactly as the app shows it, with the public sources above. Guidance only; confirm with a workshop.