C1256

BRAKE CONTROL: ELECTRONICALLY CONTROLLED BRAKE SYSTEM: 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.

HINT
DTC C1256/57 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 actuator, perform initialization of the linear solenoid valve and calibration Initialization.

HINT
When C1202/68, C1241/41, C1252/52, C1253/53 or C1391/69 are output together with C1256/57, inspect and repair the trouble areas indicated by C1202/68, C1241/41, C1252/52, C1253/53 or C1391/69 first.

PROCEDURE

1. CONFIRM DTC

(a) Confirm output DTCs Reading and Clearing Diagnostic Trouble Codes.

Result





B -- CHECK CIRCUIT INDICATED BY OUTPUT DTC Electronically Controlled Brake System
A -- Continue to next step.

2. CUSTOMER PROBLEM ANALYSIS

(a) Perform customer problem analysis to confirm whether if the customer was frequently braking when the brake warning light/yellow (minor malfunction) was illuminated.

HINT
DTC C1256/57 may be output if the accumulator pressure drops due to frequent braking (this is not a malfunction).

Result





B -- READ VALUE USING TECHSTREAM (ACCUMULATOR PRESSURE SENSOR)
A -- Continue to next step.

3. INSPECT BRAKE ACCUMULATOR PUMP

(a) Turn the power switch OFF.

(b) Disconnect the A23 and A24 accumulator connectors.





(c) Measure the resistance according to the value(s) in the table below.

Standard resistance:





NG -- REPLACE BRAKE ACCUMULATOR PUMP Removal
OK -- Continue to next step.

4. READ VALUE USING TECHSTREAM (ACCUMULATOR PRESSURE SENSOR)

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch ON (IG).

(c) Select the Data List mode on the Techstream.

ABS/VSC/TRAC:





(d) 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) for 30 seconds.

OK:

The accumulator pressure sensor voltage change is within 0.2 V.

NG -- PERFORM ACTIVE TEST USING TECHSTREAM (SMC1, SMC2, SLRRR, AND SLRRL)

OK -- USE SIMULATION METHOD TO CHECK How To Proceed With Troubleshooting

5. PERFORM ACTIVE TEST USING TECHSTREAM (SMC1, SMC2, SLRRR, AND SLRRL)

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch ON (IG).

(c) Select the Active Test mode on the Techstream.

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

- Main relay 1 and 2 are on.
- Shift lever is P position.
- Parking brake is on.
- Vehicle speed is 0 km/h (0 mph).

ABS/VSC/TRAC:





(d) Using the Techstream, turn SMC1, SMC2, SLRRR, or SLRRL ON.





(e) Check that each wheel cylinder's output value does not increase.

OK:

Each wheel cylinder's output value does not increase.

HINT
If any of wheel cylinder's output value increases, there may be a brake fluid leak in the brake actuator.

NG -- REPLACE BRAKE ACTUATOR Removal

OK -- REPLACE BRAKE ACCUMULATOR PUMP Removal