DTC C1256-56: Accumulator Low Pressure [06/2015 - ]: Procedure

1. Ask the customer if frequent braking was performed while the brake warning light / yellow (minor malfunction) was on.

   Result

   Result	Proceed to
   Frequent braking was not performed.	A
   Frequent braking was performed.	B

   HINT: 

   This DTC may be stored even if the accumulator pressure drops only temporarily due to frequent braking.

Result: 

B 

END 

Result: 

A 

See step  2

1. Make sure that there is no looseness at the locking part and the connecting part of the connectors.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Component without harness connected (Brake Booster Pump Assembly)

2. Disconnect the A35 and A36 brake booster pump assembly connectors.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A35-1 (BM1) - A35-2 (GND1)	Always	Below 10 Ω
   A36-2 (BM2) - A36-1 (GND2)	Always	Below 10 Ω
   A35-1 (BM1) - A36-2 (BM2)	Always	Below 1 Ω
   A35-2 (GND1) - A36-1 (GND2)	Always	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE BRAKE BOOSTER PUMP ASSEMBLY. Refer to  REMOVAL [06/2015 - 11/2018]  , or refer to  REMOVAL [11/2018 - ] 

Result: 

OK 

See step  3

1. Reconnect the A35 and A36 brake booster pump assembly connectors.
2. Connect the Techstream to the DLC3.
3. Turn the power switch on (IG).
4. Select the Data List on the Techstream.

   Refer to DTC CHECK / CLEAR [06/2015 - ]

   Chassis > ABS/VSC/TRAC > Data List 

   Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
   Accumulator Sensor	Accumulator pressure sensor	Min.: 0.00 V, Max.: 5.00 V	Specified value: 2.90 to 4.20 V	When brake fluid is stored in the accumulator: Accumulator pressure changes in accordance with volume of fluid stored in the accumulator

   Chassis > ABS/VSC/TRAC > Data List 

   Tester Display
   Accumulator Sensor

5. Depress the brake pedal 4 or 5 times to operate the pump motor.
6. Wait for 30 seconds without depressing the brake pedal.
7. Check that the accumulator pressure sensor output value change is within the specified range.

   OK

   Accumulator pressure sensor output value change is less than 0.55 V.

   Result

   Proceed to
   OK
   NG

Result: 

OK 

USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [06/2015 - 11/2018]  , or refer to  HOW TO PROCEED WITH TROUBLESHOOTING [11/2018 - ] 

Result: 

NG 

See step  4

1. Select the Active Test on the Techstream.

   Refer to DATA LIST / ACTIVE TEST [06/2015 - ]

   Chassis > ABS/VSC/TRAC > Active Test 

   Tester Display	Measurement Item	Control Range	Diagnostic Note
   ECB Solenoid (SMC/SRC/SCC)	Switching solenoid valve (SMC/SRC/SCC)	Solenoid ON/OFF	Operation sound of solenoid (clicking sound) can be heard ECB: Electronically Controlled Brake System

   Chassis > ABS/VSC/TRAC > Active Test 

   Tester Display
   ECB Solenoid (SMC/SRC/SCC)

   HINT: 

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

   • ABS main relay is on.
   • Shift lever is in P.
   • Parking brake is applied.
   • Vehicle speed is 0 km/h (0 mph).
2. Perform the Active Test of the solenoid using the Techstream.
3. Select the Data List on the Techstream.

   Refer to DATA LIST / ACTIVE TEST [06/2015 - ]

   Chassis > ABS/VSC/TRAC > Data List 

   Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
   Wheel Cylinder Pressure Sensor	Wheel cylinder pressure sensor	Min.: 0.00 V, Max.: 5.00 V	Brake pedal released: 0.10 to 0.90 V	Reading increases when brake pedal is depressed

   Chassis > ABS/VSC/TRAC > Data List 

   Tester Display
   Wheel Cylinder Pressure Sensor

4. Check that the output value of the wheel cylinder pressure sensor does not increase.

   OK

   The output value of the wheel cylinder pressure sensor does not increase.

   HINT: 

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

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE BRAKE BOOSTER PUMP ASSEMBLY. Refer to  REMOVAL [06/2015 - 11/2018]  , or refer to  REMOVAL [11/2018 - ] 

Result: 

NG 

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY. Refer to  REMOVAL [06/2015 - 11/2018]  , or refer to  REMOVAL [11/2018 - ]