Dtc C1391-00: Abnormal Leak In Accumulator [11/2021 - ]: Description

WARNING: This page is about a different car, the 2025 Lexus NX 350h, 2024 Lexus NX 350h, 2023 Lexus NX 350h, and 2022 Lexus NX 350h. However, it is still accessible from the selected car via links, so may be relevant.

This Dtc Is Stored If Internal Or External Brake Fluid Leaks Are Detected Due To Improper Sealing In The Brake Booster With Master Cylinder Assembly Or Brake Booster With Accumulator Pump Assembly. Internal Leaks Are Suspected If The Pump Motor Operates Frequently Without Braking.

Dtc No.	Detection Item	Dtc Detection Condition	Trouble Area	Mil	Dtc Output From	Note
C1391-00	Abnormal Leak In Accumulator	Either Of The Following Is Detected: When The Brake Pedal Is Not Depressed And The Pump Motor Is Operating, The Accumulator Pressure Sensor Value Does Not Increase A Certain Number Of Times. When The Brake Pedal Is Not Depressed And The Pump Motor Is Not Operating, The Accumulator Pressure Sensor Decrease Rate Exceeds A Certain Threshold A Certain Number Of Times.	Brake Fluid Leaks Brake Booster With Master Cylinder Assembly (Malfunctioning Internal Seal Etc.) Brake Booster With Accumulator Pump Assembly (Accumulator Internal Gas Pressure Decrease, Etc.)	Does Not Come On	Brake Booster	Output ECU: No. 1 Skid Control ECU (Brake Booster With Master Cylinder Assembly)