C1391: Brake actuator accumulator pressure leak or ABS actuator fault
What Does C1391 Mean?
C1391 is a high-signal diagnostic/code reference associated with brake actuator accumulator pressure leak or abs actuator fault. FixIt matched it to 267 NHTSA owner reports across 4 vehicle models; the strongest signal is Toyota Prius.
This page was promoted from the June 2026 ranked content-gap batch because owner-report demand is concentrated enough to deserve a full diagnostic guide. Toyota owners most often report C1391 with brake, ABS, traction-control, or accumulator/actuator warnings. Treat the code as a diagnostic direction, then confirm the exact manufacturer definition, companion codes, and live data before replacing expensive parts.
Symptoms of C1391
- ⚠️ ABS, brake, traction-control, or stability-control warning lights
- ⚠️ Longer brake pedal travel or reduced brake assist
- ⚠️ Brake actuator or pump running more often than normal
- ⚠️ Warning lights that return soon after clearing codes
Common Causes
- 🔍 Brake actuator or accumulator internal pressure leak
- 🔍 Weak brake booster pump/actuator assembly after confirming power and grounds
- 🔍 Low 12V voltage or poor module ground causing brake-control faults
- 🔍 Damaged wiring or connector at ABS/brake-control module
C1391 Reports by Year
Real Owner Reports
From NHTSA complaint database — actual owner descriptions.
"MY ABS BRAKE WARNING LIGHT CAME ON TWO DAYS AGO ALONG WITH ANOTHER BRAKE LIGHT. IT HAPPENED WHILE I WAS DRIVING SO IT WAS SCARY. I TOOK IT TO THE DEALERSHIP AND THEY SHOWED TWO CODES - C1256 AND C1391. THESE WERE PART OF A BRAKE ACTUATOR ASSEMBLY TOYOTA TECHNICAL SERVICE BULLETIN WHICH EXPIRED ON 12/31/2017. SINCE MINE"
— Toyota Prius owner, 03/27/2018
"ABS WARNING LIGHT ARE NOW ON. FEEL CAR IS LOSING BREAK CAPABILITY. NO ACCIDENT BUT DO NOT FEEL CONFIDENT WITH THE BRAKE CAPACITY. TODAY I TOOK THE CAR TO THE DEALER AND THEY STATED THAT THE ABS ACTUATOR ASSEMBLY (CODE C1391) NEED TO BE REPLACE. LOOKING IN THE INTERNET AND IT LOOKS A VERY COMMON DEFECT FOR PRIUS. THIS I"
— Toyota Prius owner, 02/28/2020
"MY VEHICLE HAS A DEFECTIVE ABS ACTUATOR, A PART PREVIOUSLY UNDER RECALL BY THE MANUFACTURER-TOYOTA. (2006 TOYOTA PRIUS ABS PART, ACTUATOR COMPLETE ASSEMBLY, ID 44510-47050) WARNING LIGHTS: MASTER WARNING ABS BRAKE SYSTEM: CODES: P0571, C1256, C1391. THIS DEFECTIVE BRAKING COMPONENT MAKES MY VEHICLE EXTREMELY UNSAFE TO"
— Toyota Prius owner, 05/15/2018
Source: NHTSA Complaints Database
Most Reported Vehicles for C1391
Based on NHTSA owner complaint data.
| # | Vehicle | Reports |
|---|---|---|
| 1 | TOYOTA PRIUS | 218 |
| 2 | TOYOTA HIGHLANDER | 29 |
| 3 | TOYOTA CAMRY | 19 |
| 4 | TOYOTA AVALON | 1 |
C1391 Reports by Vehicle
Detailed NHTSA complaint analysis for each vehicle model.
Diagnostic Tips
- Scan the ABS/brake-control module, not only the powertrain module
- Check 12V battery condition, charging voltage, fuses, and brake-module grounds
- Inspect brake actuator wiring/connectors before approving actuator replacement
- Confirm repair with a brake bleed/calibration procedure required by the OEM service manual
Common Mistakes to Avoid
- ❌ Replacing a module or safety component before checking power, ground, connectors, and companion codes.
- ❌ Using only a generic OBD-II scanner when the code is stored in ABS, SRS, body, or manufacturer-specific modules.
- ❌ Clearing the code before saving freeze-frame data and confirming whether recalls/campaigns apply.
Frequently Asked Questions
What does C1391 mean?
Is C1391 safe to ignore?
What should I check first for C1391?
What To Do Next
Possible Fixes
- 🔧 Scan the ABS/brake-control module, not only the powertrain module
- 🔧 Check 12V battery condition, charging voltage, fuses, and brake-module grounds
- 🔧 Inspect brake actuator wiring/connectors before approving actuator replacement
- 🔧 Confirm repair with a brake bleed/calibration procedure required by the OEM service manual
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1
Find your vehicle above
Click your make and model for real owner reports and common causes specific to your vehicle.
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Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
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Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.