C1391 Hybrid brake booster or actuator fault, internal brake fluid leak (Toyota, Lexus)

Hybrid brake booster or actuator fault

C1391 in short

On Toyota and Lexus hybrids, C1391 is one of four brake codes Toyota uses to confirm a fault in the hybrid brake booster or brake actuator, usually a small internal brake fluid leak. If the red brake light is on or the pedal feels wrong, stop and call a dealer; otherwise have it inspected right away.

Toyota and Lexus hybrids use an electric pump and a pressure accumulator to power the brakes. Toyota's bulletin summaries do not define C1391 on its own; a hybrid repair shop reference, not Toyota, calls it an accumulator leak.

Toyota and Lexus have issued many bulletins for hybrids that show the brake, ABS or TRAC warning lights, or a Check VSC message, with C1391, C1252, C1253 or C1256 stored. They say a small brake fluid leak inside the brake booster with master cylinder, or inside the brake actuator on other models and years, may be the cause.

On certain 2014–2016 Highlander hybrids and 2017 Prius v, Customer Support Program 24TE01 extends coverage for the brake booster and booster pump when these codes are stored. This is a brake fault, so diagnosis belongs with a dealer, not a home repair.

Pick your make

C1391 is a manufacturer-specific code: its meaning depends on who built the car.

Other makes: meaning not verified. Check with a scan tool that reads manufacturer definitions.

Most likely causes

  1. Small internal brake fluid leak in the brake booster with master cylinder

    Supported by vehicle data
    Why it ranks here
    Toyota and Lexus bulletins for the 2011–2015 Prius and Prius Plug-in, 2012–2018 Prius v, 2012–2014 Prius c, 2012–2014 Camry Hybrid and 2011–2014 CT 200h name this leak when C1391 and the brake warning lights appear.
    What would change this
    Rises on those models, and when C1391, C1252, C1253 and C1256 are stored together.

  2. Small internal brake fluid leak in the brake actuator

    Supported by vehicle data
    Why it ranks here
    Toyota and Lexus bulletins for the 2004–2009 Prius, 2006–2019 Highlander hybrids, 2007–2011 Camry HV, 2015–2017 Prius c and 2014–2017 CT 200h name an internal leak in the brake actuator for the same group of codes.
    What would change this
    Rises on those models; the bulletin for your exact model and year decides which part is meant.

  3. Low brake fluid or an outside leak

    Possible — needs testing
    Why it ranks here
    Toyota's owner's manual says the red brake light can mean low brake fluid. The bulletins describe internal leaks, so an outside leak is a separate check, not the usual cause.
    What would change this
    Rises if the reservoir level is low or there is fluid on a wheel or under the car.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Note which warning lights are on (red brake light, ABS, TRAC, Check VSC) and whether the brake pedal feels different.

    Low risk

    • IfThe red brake warning light is on or the pedal feels different

      It meansToyota says to stop in a safe place and contact a dealer. Do not keep driving.

      Go to step 4

    • IfOnly the ABS, TRAC or Check VSC warning is on

      It meansBrake assist or stability help may be off. Have it inspected right away.

      Go to step 2

  2. Have all chassis codes read with a scan tool that reads Toyota brake codes, and note whether C1391, C1252, C1253 and C1256 are stored together.

    Low riskTool: scan tool that reads Toyota chassis codes

    • IfC1391 is stored with one or more of the other three

      It meansThis matches the pattern in Toyota's bulletins for an internal leak in the booster or actuator.

      Go to step 3

    • IfC1391 is stored alone

      It meansStill have the bulletin checked, but the dealer's full diagnosis matters more.

      Go to step 3

  3. With the car parked, look at the brake fluid level through the side of the reservoir under the hood without opening it, and look for fluid at the wheels or under the car.

    Low risk

    • IfThe level is low or there is fluid outside

      It meansThere may be an outside leak. Do not drive; have it towed or checked where it sits.

      Points to: Low brake fluid or an outside leak

    • IfThe level looks normal and nothing is wet

      It meansAn internal leak, as the bulletins describe, is more likely.

      Go to step 4

  4. Have a Toyota or Lexus dealer check the VIN for the bulletin and Customer Support Program 24TE01, then follow the bulletin's diagnosis.

    Best left to a shopTool: dealer scan tool

    Warning:Dealer procedure on the hybrid brake system, which can hold high fluid pressure. Do not open or bleed it yourself.

Symptoms

  • Red brake warning light on Gets more serious: stop and have it checked.
  • ABS warning light on
  • TRAC light on or Check VSC message
  • Brake pedal feels different than normal Gets more serious: stop and have it checked.

How to fix

This is a safety-critical system, so we explain the code but don't give repair steps. Have it inspected by a qualified technician.

Parts and cost context

  • Brake booster assembly with master cylinder:Named by the newer bulletins; one repair article says the booster pump is replaced with it. Labor varies; get a quote, and ask the dealer about 24TE01 coverage first.
  • Brake actuator:Named by the bulletins for older and some later models. Labor varies; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Toyota

  • 2004–2015 · Prius

    Supported by vehicle data

    Toyota bulletins list this code with the brake, ABS or TRAC lights on 2004–2009 Prius (internal leak in the brake actuator) and 2011–2015 Prius and Prius Plug-in (internal leak in the brake booster with master cylinder). The bulletins are on NHTSA, but whether they are still current is not verified, so it is labelled vehicle data rather than confirmed.

    Where it is:Brake actuator (2004–2009) or brake booster with master cylinder (2011–2015)

  • 2006–2019 · Highlander

    Supported by vehicle data

    Toyota bulletins cover 2006–2007 Highlander HV and 2008–2019 Highlander Hybrid for an internal leak in the brake actuator, and Customer Support Program 24TE01 covers the brake booster and booster pump on certain 2014–2016 Highlander HV. Hybrid models only. The bulletins are on NHTSA, but whether they are still current is not verified, so it is labelled vehicle data rather than confirmed.

    Where it is:Brake actuator or brake booster assembly

  • 2012–2018 · Prius V

    Supported by vehicle data

    Toyota bulletins cover 2012–2018 Prius v for an internal leak in the brake booster with master cylinder, and 24TE01 adds coverage for certain 2017 models. The bulletins are on NHTSA, but whether they are still current is not verified, so it is labelled vehicle data rather than confirmed.

    Where it is:Brake booster assembly with master cylinder

  • 2012–2017 · Prius C

    Supported by vehicle data

    Toyota bulletins cover 2012–2014 Prius c (brake booster with master cylinder) and 2015–2017 Prius c (brake actuator). The bulletins are on NHTSA, but whether they are still current is not verified, so it is labelled vehicle data rather than confirmed.

    Where it is:Brake booster with master cylinder or brake actuator

  • 2007–2014 · Camry

    Supported by vehicle data

    Hybrid models only: 2007–2011 Camry HV (brake actuator) and 2012–2014 Camry Hybrid (brake booster with master cylinder). The 2012–2014 bulletin also covers the 2013–2015 Avalon Hybrid. The bulletins are on NHTSA, but whether they are still current is not verified, so it is labelled vehicle data rather than confirmed.

    Where it is:Brake actuator or brake booster with master cylinder

  • T-SB-0032-16Status unverified

    Brake, ABS and/or TRAC lights or Check VSC with C1391, C1252, C1253 or C1256

    2004–2009prius, highlander · issued · NHTSA 10134400

    2004–2009 Prius and 2006–2007 Highlander HV. Repair procedure for a small internal brake fluid leak inside the brake actuator. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • T-SB-0064-19Status unverified

    Brake, ABS and/or TRAC lights or Check VSC with C1391, C1252, C1253 or C1256

    2008–2010highlander · issued · NHTSA 10161541

    2008–2010 Highlander Hybrid. Repair procedure for a small internal brake fluid leak inside the brake actuator. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • T-SB-0041-14Status unverified

    Brake, ABS and/or TRAC lights or Check VSC with C1391, C1252, C1253 or C1256

    2007–2011camry · issued · NHTSA 10132769

    2007–2011 Camry HV. Repair procedure for a small internal brake fluid leak inside the brake actuator. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • T-SB-0024-19Status unverified

    Brake, ABS and/or TRAC lights or Check VSC with C1391, C1252, C1253 or C1256

    2011–2015prius, prius-plug-in · issued · NHTSA 10158575

    2011–2015 Prius and 2012–2015 Prius Plug-in. Repair procedure for a small internal brake fluid leak inside the brake booster assembly with master cylinder. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • T-SB-0089-20Status unverified

    Brake, ABS and/or TRAC lights or Check VSC with C1391, C1252, C1253 or C1256

    2012–2014prius-v · issued · NHTSA 10181799

    2012–2014 Prius v. Repair procedure for a small internal brake fluid leak inside the brake booster assembly with master cylinder. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • T-SB-0115-20Status unverified

    Brake, ABS and/or TRAC lights or Check VSC with C1391, C1252, C1253 or C1256

    2015prius-v · issued · NHTSA 10184562

    2015 Prius v. Repair procedure for a small internal brake fluid leak inside the brake booster assembly with master cylinder. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • T-SB-0013-23Status unverified

    Brake, ABS and/or TRAC lights or Check VSC with C1391, C1252, C1253 or C1256

    2016–2018prius-v · issued · NHTSA 10234318

    2016–2018 Prius v. A small brake fluid leak inside the brake booster assembly with master cylinder. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • T-SB-0028-21Status unverified

    Brake, ABS and/or TRAC lights or Check VSC with C1391, C1252, C1253 or C1256

    2012–2014prius-c · issued · NHTSA 10198129

    2012–2014 Prius c. Repair procedure for a small internal brake fluid leak inside the brake booster assembly with master cylinder. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • TSB000824Status unverified

    Brake, ABS and/or TRAC lights or Check VSC with C1391, C1252, C1253 or C1256

    2015–2017prius-c · issued · NHTSA 10252260

    2015–2017 Prius c. Repair procedure for a small internal brake fluid leak inside the brake actuator. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • TSB000924Status unverified

    Brake, ABS and/or TRAC lights or Check VSC with C1391, C1252, C1253 or C1256

    2014–2016highlander · issued · NHTSA 10252261

    2014–2016 Highlander Hybrid. Repair procedure for a small internal brake fluid leak inside the brake actuator. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • T-SB-0014-25Status unverified

    Brake, ABS and/or TRAC lights or Check VSC with C1391, C1252, C1253 or C1256

    2017–2019highlander · issued · NHTSA 11014208

    2017–2019 Highlander Hybrid. A small internal brake fluid leak inside the brake actuator. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • T-SB-0130-19Status unverified

    Brake, ABS and/or TRAC lights or Check VSC with C1391, C1252, C1253 or C1256

    2012–2015camry, avalon · issued · NHTSA 10165988

    2012–2014 Camry Hybrid and 2013–2015 Avalon Hybrid. Repair procedure for a small internal brake fluid leak inside the brake booster assembly with master cylinder. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • 24TE01Status unverified

    Customer Support Program: brake booster and brake booster pump assemblies

    2014–2017highlander, prius-v · issued · NHTSA 11011632

    Extra coverage for internal brake booster faults on certain 2014–2016 Highlander HV and 2017 Prius v, verified by C1391, C1252, C1253 or C1256. Repair is a new brake booster and booster pump. Primary coverage ended March 31, 2025; secondary coverage runs 10 years or 150,000 miles from first use. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Lexus

  • 2011–2017 · CT

    Supported by vehicle data

    Lexus bulletins cover the 2011–2014 CT 200h (brake booster with master cylinder) and 2014–2017 CT 200h (brake actuator). The bulletins are on NHTSA, but whether they are still current is not verified, so it is labelled vehicle data rather than confirmed.

    Where it is:Brake booster with master cylinder or brake actuator

  • L-SB-0009-21Status unverified

    Brake, ABS and/or TRAC lights or Check VSC with C1391, C1252, C1253 or C1256

    2011–2014ct · issued · NHTSA 10198130

    2011–2014 CT 200h. Repair procedure for a small internal brake fluid leak inside the brake booster assembly with master cylinder. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • LSB000824Status unverified

    Brake, ABS and/or TRAC lights or Check VSC with C1391, C1252, C1253 or C1256

    2014–2017ct · issued · NHTSA 10252263

    2014–2017 CT 200h. Repair procedure for a small internal brake fluid leak inside the brake actuator. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • C1252Hybrid brake booster or actuator fault (Toyota, Lexus) or vacuum pump control circuit (Chrysler, Jeep, Ram)

    Shares causes Supported by vehicle data

    Toyota and Lexus bulletins list C1391 and C1252 for the same internal brake fluid leak in the brake booster or actuator, so they often appear together.

  • C1253Hybrid brake booster or actuator fault, internal brake fluid leak (Toyota, Lexus)

    Shares causes Supported by vehicle data

    Toyota and Lexus bulletins list C1391 and C1253 for the same internal brake fluid leak in the brake booster or actuator, so they often appear together.

  • C1256Hybrid brake booster or actuator fault, internal brake fluid leak (Toyota, Lexus)

    Shares causes Supported by vehicle data

    Toyota and Lexus bulletins list C1391 and C1256 for the same internal brake fluid leak in the brake booster or actuator, so they often appear together.

All ABS, traction and stability control codes

C1391 questions

Is it safe to drive with C1391?

If the red brake warning light is on, Toyota says to stop in a safe place and contact a dealer. With only the ABS or stability lights, have it inspected right away.

Is C1391 covered by Toyota?

Customer Support Program 24TE01 covers the brake booster and booster pump on certain 2014–2016 Highlander hybrids and 2017 Prius v, verified by this group of codes. Ask a dealer to check your VIN.

Why are C1391, C1252, C1253 and C1256 often stored together?

Toyota's bulletins list all four for the same condition: a small internal brake fluid leak in the brake booster or brake actuator on hybrid models.

Sources and review

  1. Toyota Camry Owner's Manual (OM06291U) — Toyota
  2. Toyota T-SB-0024-19: brake, ABS, TRAC lights or Check VSC with C1391/C1252/C1253/C1256 (Prius, Prius Plug-in) — Toyota Motor Sales / NHTSA ,
  3. Toyota T-SB-0032-16: brake, ABS, TRAC lights or Check VSC with C1391/C1252/C1253/C1256 (Prius, Highlander HV) — Toyota Motor Sales / NHTSA ,
  4. Toyota T-SB-0089-20: brake, ABS, TRAC lights or Check VSC with C1391/C1252/C1253/C1256 (Prius v) — Toyota Motor Sales / NHTSA ,
  5. Toyota T-SB-0115-20: brake, ABS, TRAC lights or Check VSC with C1391/C1252/C1253/C1256 (2015 Prius v) — Toyota Motor Sales / NHTSA ,
  6. Toyota T-SB-0013-23: brake, ABS, TRAC lights or Check VSC with C1391/C1252/C1253/C1256 (Prius v) — Toyota Motor Sales / NHTSA ,
  7. Toyota T-SB-0028-21: brake, ABS, TRAC lights or Check VSC with C1391/C1252/C1253/C1256 (Prius c) — Toyota Motor Sales / NHTSA ,
  8. Toyota T-SB-0130-19: brake, ABS, TRAC lights or Check VSC with C1391/C1252/C1253/C1256 (Camry Hybrid, Avalon Hybrid) — Toyota Motor Sales / NHTSA ,
  9. Lexus L-SB-0009-21: brake, ABS, TRAC lights or Check VSC with C1391/C1252/C1253/C1256 (CT 200h) — Lexus (Toyota Motor Sales) / NHTSA ,
  10. Small Brake Fluid Leak for Toyota — VehicleServicePros (information courtesy of Mitchell 1) ,
  11. Toyota T-SB-0064-19: brake, ABS, TRAC lights or Check VSC with C1391/C1252/C1253/C1256 (Highlander Hybrid) — Toyota Motor Sales / NHTSA ,
  12. Toyota T-SB-0041-14: brake, ABS, TRAC lights or Check VSC with C1391/C1252/C1253/C1256 (Camry HV) — Toyota Motor Sales / NHTSA ,
  13. Toyota TSB000824: brake, ABS, TRAC lights or Check VSC with C1391/C1252/C1253/C1256 (Prius c) — Toyota Motor Sales / NHTSA ,
  14. Toyota TSB000924: brake, ABS, TRAC lights or Check VSC with C1391/C1252/C1253/C1256 (Highlander Hybrid) — Toyota Motor Sales / NHTSA ,
  15. Toyota T-SB-0014-25: brake, ABS, TRAC lights or Check VSC with C1391/C1252/C1253/C1256 (Highlander Hybrid) — Toyota Motor Sales / NHTSA ,
  16. Lexus LSB000824: brake, ABS, TRAC lights or Check VSC with C1391/C1252/C1253/C1256 (CT 200h) — Lexus (Toyota Motor Sales) / NHTSA ,
  17. Toyota Customer Support Program 24TE01: brake booster and brake booster pump assemblies — Toyota Motor Sales / NHTSA ,
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Written by
Saurabh K.
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