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Home >> Lexus >> 2021 >> LS 500h RWD >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Electronically Controlled Brake System (W/O Advanced Park) - Diagnostic Codes (2 Of 3) >> ELECTRONICALLY CONTROLLED BRAKE SYSTEM (w/o Advanced Park) >> DTC C1256: Accumulator Low Pressure [10/2020 - 10/2023] >> Description

DTC C1256: Accumulator Low Pressure [10/2020 - 10/2023]: Description

The accumulator pressure sensor is built into the brake actuator assembly and detects the accumulator pressure.

The skid control ECU assembly turns on the brake warning light / yellow (minor malfunction), and sounds the meter buzzer if it senses a decrease in the accumulator pressure.

DTC C1256 may be stored if the accumulator pressure drops due to frequent braking (this is not a malfunction).

DTC No. Detection Item INF Code DTC Detection Condition Trouble Area MIL Note
C1256 Accumulator Low Pressure 141
143
  • INF Code: 141
    • Either of the following is detected:
      1. After the startup routine of the skid control ECU assembly has completed, the accumulator pressure is 6 MPa (61.2 kgf/cm2 , 870 psi) or less for 3 seconds or more.
      2. When the accumulator pressure is not being consumed by brake operation and the pump motor is running, the accumulator pressure does not exceed 0.25 MPa (2.5 kgf/cm2 , 36 psi) for between 1.698 and 9 seconds (varies depending on auxiliary battery voltage).
      3. The accumulator pressure is 14.62 MPa (149.1 kgf/cm2 , 2121 psi) or less for between 33 seconds and 99 seconds (varies depending on auxiliary battery voltage).
      4. When the vehicle speed is 3 km/h (2 mph) or more, the brake pedal is depressed and the brake force is less than 0.25 G, the accumulator pressure is less than 12 MPa (122.4 kgf/cm2 , 1741 psi) for 0.348 seconds.
  • INF Code: 143
    • When the brake pedal is depressed and the brake force is less than 0.25 G, the accumulator pressure is less than 12 MPa (122.4 kgf/cm2 , 1741 psi) for 0.348 seconds.
  • INF Code: 141
    • Accumulator pressure dropped due to frequent brake pedal operation (not a malfunction)
    • Pump motor malfunction
    • Accumulator deterioration
    • Brake fluid leaks
    • Accumulator pressure sensor
    • Supply voltage reduced
  • INF Code: 143
    • Accumulator pressure dropped due to frequent brake pedal operation (not a malfunction)
    • Pump motor malfunction
    • Accumulator deterioration
    • Accumulator pressure sensor
    • Supply voltage reduced
 Comes on
(When only SAE code C1256 is stored)		 INF Code 141 (1), (2) or (3): SAE Code C1256
DTC DETECTION CONDITIONS: C1256 INF CODE: 141

  Vehicle Condition
Pattern 1 Pattern 2 Pattern 3 Pattern 4
Diagnosis Condition - - - - -
Malfunction Status After the startup routine of the skid control ECU assembly has completed, the accumulator pressure is 6 MPa (61.2 kgf/cm2 , 870 psi) or less. ◦ - - -
When the accumulator pressure is not being consumed by brake operation and the pump motor is running, the accumulator pressure does not exceed 0.25 MPa (2.5 kgf/cm2 , 36 psi). - ◦ - -
The accumulator pressure is 14.62 MPa (149.1 kgf/cm2 , 2121 psi) or less. - - ◦ -
When the vehicle speed is 3 km/h (2 mph) or more, the brake pedal is depressed and the brake force is less than 0.25 G, the accumulator pressure is less than 12 MPa (122.4 kgf/cm2 , 1741 psi). - - - ◦
Detection Time 3 seconds or more 1.698 and 9 seconds (varies depending on auxiliary battery voltage) 33 seconds and 99 seconds (varies depending on auxiliary battery voltage) 0.348 seconds or more
Number of Trips 1 trip 1 trip 1 trip 1 trip
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