Electronically Controlled Brake System

BRAKE CONTROL / DYNAMIC CONTROL SYSTEMS: ELECTRONICALLY CONTROLLED BRAKE SYSTEM: C1256/56: Accumulator Low Pressure
C1256/56 - 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 / red (malfunction) and brake warning light / yellow (minor malfunction), and sounds the meter buzzer if it senses a decrease in the accumulator pressure.

DTC C1256/56 may be output if the accumulator pressure drops due to frequent braking (this is not a malfunction).





WIRING DIAGRAM

Refer to DTCs C1252/52 and C1253/53 C1252.

INSPECTION PROCEDURE

NOTICE:
When replacing the brake booster with master cylinder (brake actuator), perform initialization and calibration of the linear solenoid valve Initialization.

HINT
When C1202/68, C1241/41, C1252/52, C1253/53 and/or C1391/69 are output together with C1256/56, inspect and repair the trouble areas indicated by C1202/68, C1241/41, C1252/52, C1253/53 and/or C1391/69 first C1202, 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:





Text in Illustration





NG -- REPLACE BRAKE BOOSTER PUMP Removal
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 on the Techstream Data List / Active Test.

ABS/VSC/TRAC





(e) Wait for 30 seconds without depressing the brake pedal.

(f) Check that the accumulator pressure sensor output values change is within the specified range.

OK:

Accumulator pressure sensor output values change is within 0.55 V.

NG -- PERFORM ACTIVE TEST USING TECHSTREAM (SOLENOID VALVE)

OK -- CHECK FOR INTERMITTENT PROBLEMS How To Proceed With Troubleshooting

4. PERFORM ACTIVE TEST USING TECHSTREAM (SOLENOID VALVE)

(a) Select the Active Test on the Techstream Data List / Active Test.

HINT
The Active Test can be performed when the following conditions are met.

* ABS main relay is on.
* Park (P) is selected.
* Parking brake is applied.
* Vehicle speed is 0 km/h (0 mph).

ABS/VSC/TRAC





*: Electronically Controlled Brake System

(b) Perform the Active Test of the solenoid using the Techstream.

(c) Select the Data List on the Techstream Data List / Active Test.

ABS/VSC/TRAC





(d) Check that the output value of the wheel cylinder does not increase.

OK:

The output value of the wheel cylinder does not increase.

HINT
If any output value increases, there may be brake fluid leaks in the brake actuator.

NG -- REPLACE BRAKE BOOSTER WITH MASTER CYLINDER Removal

OK -- REPLACE BRAKE BOOSTER PUMP Removal