C1256

BRAKE CONTROL: ELECTRONICALLY CONTROLLED BRAKE SYSTEM: C1256/57: Accumulator Low Pressure

DTC C1256/57 - Accumulator Low Pressure

DESCRIPTION

The accumulator pressure sensor is built into the actuator and detects the accumulator pressure.
The skid control ECU turns on the brake warning light / yellow (minor malfunction) and sounds the skid control buzzer if it senses a decrease in the accumulator pressure.
DTC C1256/57 may be output if the accumulator pressure drops due to frequent braking (this is not a malfunction).






WIRING DIAGRAM





INSPECTION PROCEDURE
NOTE: When replacing the skid control ECU or brake actuator assembly, perform initialization and calibration of the linear solenoid valve. Initialization
HINT: When C1241/41, C1252/52 and/or C1253/53 are output together with C1256/57, inspect and repair the trouble areas indicated by C1241/41, C1252/52, C1253/53 and/or C1391/69 first C1241, C1252, or C1391).

PROCEDURE

1. BRAKE PROBLEM CHECK
(a) Ask the customer if frequent braking was performed while the brake warning light / yellow (minor malfunction) was on.
OK:





HINT: This DTC is output even if the accumulator pressure drops only temporarily due to frequent braking.

B -- END
A -- Continue to next step.
2. INSPECT BRAKE BOOSTER PUMP
(a) Make sure that there is no looseness at the locking part and the connecting part of the connectors.





(b) Disconnect the brake booster pump connectors.
(c) Measure the resistance according to the value(s) in the table below.
Standard resistance:






NG -- REPLACE BRAKE BOOSTER PUMP
OK -- Continue to next step.
3. READ VALUE USING TECHSTREAM (ACCUMULATOR PRESSURE SENSOR)
(a) Reconnect the brake booster pump connectors.
(b) Connect the Techstream to the DLC3.
(c) Turn the power switch on (IG).
(d) Select the Data List mode on the Techstream. Data List / Active Test

ABS / VSC / TRAC:





(e) Depress the brake pedal 4 or 5 times to operate the pump motor, and check the output value on the Techstream with the motor stopped (not braking).
OK:
Accumulator pressure sensor output voltage does not drop.
NG -- READ VALUE USING TECHSTREAM (PRESSURE SENSOR)
OK -- Continue to next step.
4. RECONFIRM DTC
(a) Clear the DTCs.
(b) Perform a road test.
(c) Check if the same DTC is recorded.
Result:






B -- REPLACE SKID CONTROL ECU
A -- CHECK FOR INTERMITTENT PROBLEMS (SYMPTOM SIMULATION)
5. READ VALUE USING TECHSTREAM (PRESSURE SENSOR)
(a) Select the Data List mode on the Techstream. Data List / Active Test

ABS / VSC / TRAC:





(b) Select the Active Test mode on the Techstream. Data List / Active Test
HINT: The Active Test can be performed when the following conditions are met.
- ABS main relays 1 and 2 are on.
- Shift lever is in P.
- Parking brake is applied.
- Vehicle speed is 0 km/h (0 mph).

ABS / VSC / TRAC:





*: Electronically Controlled Brake System
(c) Perform the Active Test of the solenoid using the Techstream.





(d) Check that the output value of each wheel cylinder does not increase.
OK:
The output value of each wheel cylinder does not increase.
HINT: If any output value increases, there may be a brake fluid leak in the brake actuator.

NG -- REPLACE BRAKE ACTUATOR ASSEMBLY
OK -- REPLACE BRAKE BOOSTER PUMP