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Home >> Lexus >> 2019 >> LS 500 Base, AWD >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Electronically Controlled Brake System (W/O Vacuum Brake Booster) - Diagnostic Codes (1 Of 3) >> ELECTRONICALLY CONTROLLED BRAKE SYSTEM (w/o Vacuum Brake Booster) >> DTC C1256: Accumulator Low Pressure [12/2017 - 10/2023] >> Description

DTC C1256: Accumulator Low Pressure [12/2017 - 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 Note
C1256 Accumulator Low Pressure 141
143
  • INF Code: 141
    • Either of the following is detected:
      1. When inputting the vehicle speed, the brake operation is input with the accumulator pressure low or the accumulator pressure extremely decreased while braking for 0.3 seconds or more.
      2. The accumulator pressure has been low since system start and pressure is less than 14.62 MPa (149.1 kgf/cm2 , 2121 psi) for 120 seconds or more.

        (Stores the DTC after the conditions are met, and sounds buzzer.)

  • INF Code: 143
    • Any of the following is detected:
      1. When inputting the vehicle speed, any of the wheel cylinder pressure sensor values is lower than the specified value with the accumulator pressure low for 0.5 seconds or more.
      2. The accumulator pressure decreased without increasing the wheel cylinder pressure of each wheel.
      3. With the ABS motor relay abnormal or off, the accumulator pressure is less than 14.62 MPa (149.1 kgf/cm2 , 2121 psi) for 0.5 seconds or more.
  • 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
 -
DTC DETECTION CONDITIONS: C1256 INF CODE: 141

  Vehicle Condition
Pattern 1 Pattern 2 Pattern 3
Diagnosis Condition When vehicle speed is input ◦ ◦ -
Malfunction Status A brake pedal operation is input with the accumulator pressure low ◦ - -
A significant drop in accumulator pressure occurs while braking - ◦ -
The accumulator low pressure condition (less than 14.62 MPa (149.1 kgf/cm2 , 2121 psi)) continues from system startup - - ◦
Detection Time 0.3 seconds or more 0.3 seconds or more 120 seconds or more
Number of Trips 1 trip 1 trip 1 trip
DTC DETECTION CONDITIONS: C1256 INF CODE: 143

  Vehicle Condition
Pattern 1 Pattern 2 Pattern 3 Pattern 4
Diagnosis Condition When vehicle speed is input ◦ - - -
Malfunction Status The accumulator pressure is low and any of the wheel cylinder pressure sensor values is lower than the target ◦ - - -
The accumulator pressure is low and the wheel cylinder pressure for each wheel does not increase - ◦ - -
The ABS motor relay malfunction status continues and the accumulator pressure is less than 14.62 MPa (149.1 kgf/cm2 , 2121 psi) - - ◦ -
The ABS motor relay remains off and the accumulator pressure is less than 14.62 MPa (149.1 kgf/cm2 , 2121 psi) - - - ◦
Detection Time 0.5 seconds or more - 0.5 seconds or more 0.5 seconds or more
Number of Trips 1 trip 1 trip 1 trip 1 trip
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