C1391 on Toyota vehicles

A model year is listed because the code is named in its own record — a bulletin filed against it, or an owner’s complaint about it — not because every one of these vehicles sets it. Counts are documents in NHTSA’s files, not failure rates.

Owners’ own words, scrubbed of anything identifying. Unverified reports filed with NHTSA — what was said, not a finding that it was true.

Bulletins and campaigns Toyota filed with NHTSA whose summary names C1391. Quote the document number at the service desk — it is a diagnosis the maker has already written down.

• TSB000924 Service bulletin
  2024-02-21 · Service Brakes
• TSB: Some 2014 ? 2016 model year Highlander Hybrid vehicles may exhibit a condition in which the brake, ABS, and/or TRAC warning lights are on and/or a Check VSC message displays. One or more of the following specific Diagnostic Trouble Codes (DTCs): C1391, C1252, C1256, and/or C1253 will be stored in the vehicle memory to be used as verification. This condition may be caused by a small internal b
• 24TE01 Service campaign
  2024-11-04 · Service Brakes
• This Customer Support Program provides coverage as it applies to Brake Booster and Brake Booster Pump Assemblies on Certain 2014-2016 Model Year Highlander HV and certain 2017 Model Year Prius V Vehicles. The specific condition covered by this program is related to certain internal malfunctions of the Brake Booster Assembly. One or more of the following specific Diagnostic Trouble Codes (DTCs) C13
• TSB000824 Service bulletin
  2024-02-21 · Service Brakes
• TSB:Some 2015 ? 2017 model year Prius C vehicles may exhibit a condition where the brake, ABS, and/or TRAC warning lights are on and/or a Check VSC message displays. One or more of the following Diagnostic Trouble Codes (DTCs): C1391, C1252, C1256, or C1253 will be stored in the vehicle memory to be used as verification. This condition may be caused by a small internal brake fluid leak ins
• T-SB-0014-25 Service bulletin
  2025-01-29 · Service Brakes
• Some 2017 – 2019 model year Highlander Hybrid vehicles may exhibit a condition in which the brake, ABS, and/or TRAC warning lights are on and/or a Check VSC message displays. One or more of the following specific Diagnostic Trouble Codes (DTCs): C1391, C1252, C1256, and/or C1253 will be stored in the vehicle memory to be used as verification. This condition may be caused by a small internal brake
• T-SB-0013-23 Service bulletin
  2023-03-09 · Lane Departure
• TSB: Some 2016 ? 2018 model year Prius V vehicles may exhibit a condition where the brake, ABS, and/or TRAC warning lights are on and/or a Check VSC message displays. One or more of the following Diagnostic Trouble Codes (DTCs) C1391, C1252, C1256, and/or C1253 will be stored in the vehicle?s memory to be used as verification. This condition may be caused by a small brake fluid leak inside the bra

A stored code names the test that failed, never the part that caused it. The record above is what Toyota and its owners have filed about it; the code’s page across every make has the whole file.